Since the Digimon Franchise grew exponentially between the original series that ran from 1999 to 2000 and the current adventure held in 2020 and 2021, there are a ton more Digimon to utilize ranging from Digimon originating from later anime, to Digimon that rarely get showcased at all. However they still come as a big surprise for a show that seemingly follows the original. (Beware of spoilers)
- Algomon/Argomon was originally the Big Bad of Digimon Savers the Movie: Ultimate Power! Activate Burst Mode!!. He of all Digimon was brought back here, given his own evolution line, and even became the Starter Villain no less! Also unexpected is that they actually stick around for the Great Cataclysm arc as The Dragon to the actual Big Bad of the series, with Algomon's usual humanoid appearance coming back in a much later episode.
- Armor level Digimon are also making an appearance in this series, as regular wild/enemy Digimon. While this has happened before in other series, their appearance in this series is notable due to it being a reboot of the original Digimon Adventure series, while Armor level Digimon didn't exist yet until the Adventure 02 series.
- The appearance of Soundbirdmon, a Digimon that has its origins in the Digimon Fusion continuity, albeit as part of a fan contest only.
- Valdurmon/Varodurumon was unexpected, let alone as one of the Big Goods, due to its relative lack of plot relevance in official materials, whether they be anime, manga or video games.
- In the same episode where Valdurmon is revealed, the Holy Digimon that fought the forces of darkness alongside Valdurmon have a few surprises in store. Seraphimon, Ofanimon and Cherubimon at least make sense due to their status as the Three Great Angels, and the former two are the canonical Ultimate/Mega levels of the protagonists' Patamon and Tailmon/Gatomon, but seeing relatively minor Digimon like SlashAngemon and ClavisAngemon alongside them was a bit of a shock, especially since this is the latter's first appearance in an official Digimon anime. The biggest surprise of them all was Rasielmon, due to being a Digimon that wasn't even a thing in the original continuity until over a decade later, not to mention its Adult/Champion level Meicoomon's nature as a Tyke Bomb and its corrupted evolution into the much more destructive Raguelmon.
- All of which are a reference to the Angelic Choirs, a hierarchy of angels.
- No one expected the Perfect/Ultimate stages to be achieved by the protagonists just 10 episodes in here compared to their original counterparts who only had it happen from the 20 episode mark onwards. This is implied to be because the partner Digimon are reincarnations of Ultimate/Mega Digimon and thus already have this stage at least partially unlocked, simply needing their humans' emotions to access them.
- Neemon of Digimon Frontier fame appears in Episode 11, though this time presented as far wiser than his kooky counterpart. Scorpiomon/SkullScorpiomon also makes an appearance in the very same episode, despite being a Digimon that's often snubbed from appearing in much Digimon media due to the complexity of his nonhuman design.
- Mugendramon/Machinedramon appearing in MetalGreymon's evolution sequence to imbue Greymon with mechanical data was greatly unexpected, especially given the role said Digimon has in the original series, and how Agumon never evolves into Mugendramon as their final form despite being an option in other media. Some wonder if this implies that Digimon will branch out into other evolution lines, at least for their Dark Evolutions. This ultimately turned out to be foreshadowing for Agumon's Dark Ultimate transformation in Episode 24.
- An actual enemy Mugendramon later appeared as an antagonist, well into the anime's run.
- While new Digimon are in part expected from a new series, nobody could've foreseen Orochimon, a relatively minor Digimon in all continuities, not only joining as a noteworthy antagonist, but gaining new Adult and Ultimate forms in his evolution line in the form of Eyesmon and Nidhoggmon.
- Digimon that are the same species as ones who served as main characters from different series making a cameo isn't too much a stretch at this point. However, Episode 19 not only features a heroic Falcomon with the Digimon Savers design, but also its evolution Peckmon, three of them serving as transport. Troopmon, enemy soldiers from Digimon Xros Wars, also make a rather peculiar appearance in the very same episode, along with a cameo from Spadamon, another Digimon debuted in Xros Wars, and Valvemon/Bulbmon, an old Digimon whose first anime debut was also in Xros Wars.
- In the very same episode, three major villains directly under Devimon are introduced, SkullKnightmon of Digimon Xros Wars fame, and Calmaramon and Velgrmon/Velgemon from Digimon Frontier. Fans of the Digimon series should be aware that these three Digimon only exist under VERY specific circumstances, Calmaramon and Velgrmon themselves both being Beast Spirits, the latter a corrupted one accessed by a human. As for SkullKnightmon, it's a major antagonist in Xros Wars that Xrosses into DarkKnightmon/AxeKnightmon when paired with a DeadlyAxemon, but here it's able to evolve into DarkKnightmon without DeadlyAxemon's help. And furthermore, it ends up becoming a major antagonist and following them straight into the next arc, kidnapping and nearly sacrificing Hikari before turning out to be a corrupted Tailmon.
- And speaking of SkullKnightmon, he gets his own steed in the form of DarkMaildramon, seemingly in reference to the regular Maildramon being the steed of Knightmon. Maildramon is already a rather underutilized Digimon, last seen in the Digimon Xros Wars manga, so seeing it get a virus variation came as a slight shock.
- Episode 21 has the return of Splashmon from Xros Wars, though this case is especially unique as it's primarily in its bestial Darkness Mode 2 form, which was typically reserved for desperate battles as opposed to the more commonly used human form.
- Show of hands. How many of you were expecting ElDoradimon to be the carrier of Devimon's castle as revealed in Episode 21?
- X-Antibody Digimon have never made a true appearance in any mainline anime series until now (not counting natural carriers that also appeared in this series like the Funbeemon line and the aforementioned ClavisAngemon). Even if it is just their parts.
- Episode 21 had a completely unexpected new augment for MetalGreymon, gaining the Alteros from Virus MetalGreymon X to replace his right arm in a new form called MetalGreymon Alteros Mode.
- Episode 22 has a similar case happen to WereGarurumon in where he gains his X counterpart's wings, resulting in a new form called WereGarurumon Sagittarius Mode.
- Despite the loads and loads of surprise appearances of obscure or noteworthy Digimon making appearances all throughout Digimon 2020, absolutely nobody guessed that Moon=Milleniumon from the Wonder Swan games would serve as The Man Behind the Man to Devimon, as their silhouette appears in a flash within their crystal when NeoDevimon is born and appears to be the one responsible for cases like Nidhoggmon.
- On the subject of the Millenniummon line, due to its involvement in the plot, it was somewhat of a no-brainer that ZeedMillenniummon would make an appearance. It does so in episode 31's flashback, but there's a catch: ZeedMillenniummon lacks the bands that suppress its power.
- Episode 24 has both Mugendramon and WarGreymon debut as Ultimate levels for defeating DoneDevimon, even if one is made of deep red aura and missing the back cannons and the other is more a silhouette. In a welcome and refreshing twist to the breakneck pace of 2020's formula, neither WarGreymon nor Mugendramon were actually completed in their introductions or even unlocked by Agumon in the end.
- Episode 26 has a surprise when a Seadramon kills and eats an Ebidramon, then evolves into its next stage. Series veterans would immediately assume that it would turn into MegaSeadramon, which is frequently touted as Seadramon's canonical Perfect level. What we see instead is WaruSeadramon note , a darker-colored MegaSeadramon introduced in the first Digimon World that continually gets minor roles in video games, but was never utilized in any anime or manga and only recently got included in one of the v-pets. The WaruSeadramon then engages in a tag-team with a MegaSeadramon before being joined by more of each, which also comes across as surprising considering the two species are often at each other's throats due to the former's more conniving nature, such as the recent Digimon World -next 0rder- which had a WaruSeadramon wreak havoc and blame a MegaSeadramon for its wrongdoings.
- Episode 31 gives us a character that hasn't appear in any Digimon media for almost 20 years: GOKUMON/REAPERMON, whose first and last major appearance is the 2001 PlayStation 1 game Digimon Rumble Arena. And to top it off, it's an Ultimate evolution in the Bakemon line, which itself also creates a surprise, as the Bakemon first evolve into not the ordinary Phantomon which is its usual evolution, but MetalPhantomon, a metal variation whose only other anime appearance was back in Digimon Data Squad in 2006-2007.
- Episode 32 has Patamon evolve into his Adult form, but it is not Angemon like normal due to exhausting that form's power against DarkKnightmon. Instead, he becomes Pegasmon/Pegasusmon, his Armor Evolution that could initially only be reached via the Digimental/Digi-Egg of Hope, and even then only three years later. The 2020 Digivice toy spoiled this months before it happened, however.
- From the same episode, the Monster of the Week this time around is a Cerberumon leading a pack of Fangmon. Fangmon is a Digimon introduced in 2002's D-Scanner line that never got a major appearance until that particular episode.
- Episode 35's Digimon Encyclopedia (where a major Digimon on the heroes' side or otherwise is described in extra detail) usually gives a preview of the Digimon that's getting one of these in the next episode. The silhouette here is none other than BlitzGreymon, the virus counterpart to WarGreymon, which comes as a surprise not just because WarGreymon had already been unlocked, but Mugendramon is already confirmed to be its Dark Evolution. It's a bit of a Zigzagged Trope however, as virus-type Digimon are not necessarily evil (as the entire Guilmon line except Megidramon can attest to), and BlitzGreymon itself is effectively a role-swap that makes WarGreymon a cyborg like MetalGarurumon, who in turn has its own golden warrior variant in CresGarurumon. It's also entirely possible that Alterous Mode (achieved by overcoming/controlling the miasma/corruption against Splashmon) was hinting at BlitzGreymon, leading people more inherently familiar with Digimon to guess that BlitzGreymon (alongside CresGarurumon and subsequently Omegamon Alter-S (see the WMG section)) were set to appear, so this is more along the lines of I Knew It! in that case (in fact, CresGarurumon did later appear in episode 56). What actually makes BlitzGreymon's appearance unexpected is how early it appears, since we just got WarGreymon 5 episodes prior, and that MetalGarurumon and the other Chosen Children's Ultimate forms are still nowhere in sight at that time. Either that, or the production team is just teasing the viewers and that BlitzGreymon will not appear in episode 36 (or perhaps just as a silhouette like how WarGreymon first appeared), and that they are just confirming that yes, Agumon and Gabumon (And if the 2020 Digivice toy is to be believed, Tailmon will also be getting Holydramon/Magnadramon as an alternate Ultimate alongside Ophanimon) will be receiving alternate Ultimate forms.
- BlitzGreymon did eventually appear in Episode 36 as a new Ultimate for Agumon, with CresGarurumon following suit 20 episodes later to fill the same role for Gabumon. However, like with Pegasusmon, the 2020 Digivice toy spoiled both of these instances months in advance.
- Episode 38 features yet another reappearance of Xros Wars Digimon, this time it's the Pickmon group, a bunch of small star-like Digimon. Pickmons are extremely underutilized in Xros Wars, so while their reappearance here isn't that huge either, it's the fact that the writers even remember them in the first place that makes their reappearance rather notable.
- Episode 38 also features the very first anime appearance of Vi-Elecmon, a Digimon whose debut was back in Digimon Digital Card Battle PlayStation 1 game released in 2000-2001, and until this episode, has never appeared anywhere else. Although the currently ongoing Digimon ReArise mobile game does feature an evolution line for Vi-Elecmon (which has it evolving into either Triceramon or Qinglongmon/Azulongmon), at the time the episode preview for 38 aired, the Vi-Elecmon itself was not obtainable yet, existing only as portrait in the evolution tree, meaning technically it's not in the game yet, making this anime appearance more notable.
- Episode 39 brings multiple unexpected appearance from various Digimon, such as Burgamon, Muchomon (who has never appeared in anime series before), and even Pusurimon from Digimon ReArise, whose circumstance regarding its existence in ReArise made its cameo appearance in this anime series a peculiar one.
- This poster for the anime
◊ displays the characters with their Digimon partners in their Ultimate forms. To the sides are Takeru and Hikari, with Holydramon appearing above Hikari to hint that this is the Ultimate form Tailmon gets first. Beneath Takeru, however, is Goddramon/Goldramon, a fellow Great Dragon alongside Holydramon, hinting that this is a potential Ultimate for Patamon. Unlike Holydramon and fellow Great Dragons Qinglongmon and Megidramon (the former of which being one of the Holy Beasts and the other being the Dark Evolution of Guilmon), Goddramon was never featured in a major way, with the one time it did appear as an important character being in a crossover between V-Tamer and Frontier; and even then, it was a Metamormon pretending to be Goddramon. Here however, it's the Ultimate level of one of the main characters' Digimon, making it a massive curveball for those not anticipating it. And to top it all off, it wasn't even spoiled by the 2020 Digivice toy like Pegasmon/Pegasusmon, BlitzGreymon and CresGarurumon were! Sure enough, they debut proper in episode 50. - Alongside Episode 43 featuring the return of Etemon and Volcamon, another "alternate" evolution for a chosen Digimon is introduced without warning, one that was not shown or hinted at in anything prior to the episode’s airing: Palmon digivolves into Ponchomon. It’s especially rather surprising, considering Ponchomon is one of Patamon's official armor evolutions.
- Episode 44 has the titular forest actually be Petaldramon's back.
- One of Sephirothmon/Sakkakumon's spheres appears in Episode 46. Yes, just one. Operating as separate spheres is something that not even its Frontier counterpart did.
- Episode 47 has Minidekachimon as half of the episode's Big Bad Duumvirate, with its evolution Atamadekachimon acting as its Horse of a Different Color. Atamadekachimon hasn't appeared since 2007, where it existed solely as Temporary Online Content for the DigiWindow. Minidekachimon originally only existed as part of Atamadekachimon's sprite and description but the episode reverses this, placing greater focus on it with Atamadekachimon playing second fiddle.
- In addition, the baby Digimon that were with Nohemon in the well includes Wanyamon, Pusumon, and Pinamon, all making their anime debut. Wanyamon made numerous appearances in games, but never in the anime until now. For Pinamon, this episode is its first appearance outside of the virtual pets ever. As for Pusumon, it's the Baby I form of Pusurimon (see the Episode 39 section above).
- In Episode 49, a Griffomon/Gryphonmon is spawned from the data mass that would become Millenniummon and becomes the episode's main threat. Its anime appearances beforehand were limited to a cameo in Tamers and a minor role in Frontier.
- While unnamed, episode 50 has Millenniummon go One-Winged Angel into ZeedMillenniummon in response to Goddramon/Goldramon and Holydramon/Magnadramon. However, it has its Power Limiter bands on.
- The Monster of the Week of Episode 51 is Burpmon. This especially jarring considering that Burpmon only appeared in one version of V-pets and is a punishment for improperly raising your Digimon, similar to Numemon and Scumon/Sukamon. It didn’t even have a level or official profile yet at the time it was shown, and even after it got its profile, it still doesn't have an official level or attribute.
- In the same episode, not only is Pucchiemon/Bucchiemon among the Digimon found in the tree the episode takes place in (itself underutilized despite being Wormmon's Digimental of Kindness evolution, which is based on Ken's own crest), but its barely-showcased green variation is present as well.
- Not the characters per se, since they were all already announced, but did you really expect Palmon to get her mega evolution before both Gomamon and Tentomon?
- Episode 54 gives a flashback cameo of Tekkamon, who previously had only appeared in the Digimon World games as a reskin of Giromon.
- Episode 56 gives a couple of surprises with the main one being Strabimon, a Digimon known to evolve into Digimon Frontier's Wolfmon/Lobomon, but unlike Flamon who evolves into Agnimon/Agunimon in a similar fashion, had never appeared in an adaptation before. This marks Strabimon's very first appearance in any major Digimon media. Among the background Digimon, a Koemon/Monmon can also be seen; Koemon's claim to fame was Digimon World 3 and nothing else, so seeing it finally get acknowledged with an animated appearance was a pleasant surprise.
- Episode 58 shows the very first anime appearance of SkullBaluchimon, a Digimon whose debut in the franchise was all the way back in 2003.
- Episode 59 features a GranKuwagamon note as major enemy, which is a notable appearance as prior to this, all its anime appearance only amounts to a short cameo, despite being a rather well-known Mega level Digimon.
- Episode 60 and 61 each features the reappearance of Olegmon and Gravimon, both from the 2010-2011 series Digimon Xros Wars. Gravimon in particular, is especially notable because unlike his Xros Wars incarnation who is evil through and through, this Gravimon is merely a neutral bystander with pessimistic view, that eventually acts as an ally for Takeru after being convinced by Takeru's hope, helping him to bring ElDoradimon back to Cloud Continent.
- Episode 63 has the first anime debut of Valkyrimon, a well-known Mega level Digimon that has appeared in multiple games, but never appeared in anime until now. However, aside from its broken statue, most of its appearance has it covered in light, although it's still made very clear that it's Valkyrimon.
- Among the evil Digimon attacking the Tree of Knowledge in episode 64 is the Digimon World version of Golemon (also known as Rockmon). This wireframe beastie hasn't appeared in any Digimon media since the turn of the millennium. The Soundbirdmon create them from the junk data stored at the tree.
- HolyAngemon Priest Mode also briefly appears as part of Seraphimon's evolution sequence, having this episode as this form's very first anime appearance ever since it first showed up in the franchise through physical card game (and even then, just once, no reprint!) and V-Tamer manga, all the way back in 1998. It never appeared anywhere else since then, until now.
- Episode 67 brings one last surprise appearance with a Phascomon among the young Digimon being taught by Wisemon and Gerbemon. Phascomon is an evil drop bear that acts as Belphemon's Rookie form, only this one isn't evil and is just as innocent as the other Digimon assembled.
