WMG / Equestria Girls: Sonic the Hedgehog

Shadow is a product of Equestrian magic.

• Considering Princess Celestia and Starswirl the Bearded have traveled the Multiverse as shown in the IDW comics, they could've at some point landed in the human version of Equestria where G.U.N found them; and promised to release them in exchange for their secrets on magic. It could be possible that Shadow was created from Starswirl and Celestia's magic.
  • It depends on how much author sees comics as canon to the show. However, that doesn't mean he can't include this bit into his fanfic.

Fluttershy and Rainbow Dash will also get Ship Tease either in the second or third movie

• With Sunset/Sci-Twi and Rarity/Applejack getting Ship Tease so far in the adaptation of the second movie, there is a possibility of Rainbow Dash and Fluttershy getting some as well. Especially with how the group split up in the motel room arrangements in the first movie with Sunset and Sci-Twi sharing a room and same going for Rarity and Applejack with Rainbow Dash and Fluttershy sharing a room as well.

Knuckles will be the closest to Applejack among the Rainbooms

• Between the main Sonic trio, they so far parallel:
  • Sonic to Sunset and Rainbow Dash, being orphans from another world like the former and a cocky speedster like the latter.
  • Tails to Twilight as The Smart Guy among the group and forming a close bond with the person (Sonic and Sunset) from another world (albeit Sunset/Sci-Twi lean toward a romantic one while Sonic and Tails lean to a brotherly one).
• And so far the second movie seems to be indicating Applejack will be more in the spotlight than the last movie, giving indication she could end up being the Rainboom closest to Knuckles, potentially bonding over having lost family they knew in the past (Applejack with her parents and Knuckles with his family and ancestors) and being warriors of strength among their groups.

The Rainbooms will get an upgrade from the Master Emerald.

• Given how powerful Robotnik will become once he gains the Master Emerald, the Rainbooms will then get empowered by the gem themselves to amplify their geodes to get super states of their own.

Bon Bon is an undercover agent.

• Similar to how her pony counterpart was an undercover agent sent to take care of a monster, Bon Bon/Sweetie Drops may be working undercover to keep an eye on Sonic due to working for S.M.I.L.E. (Secret Monster Intelligence League of Equestria), which may be a black-ops unit of G.U.N.

The Dazzlings will pull a Heel–Face Turn.

• Upon seeing how far Cinch is willing to go or how much of a crazed lunatic Robotnik is, the Dazzlings will have a change of heart and decide to, albeit reluctantly, join the heroes to take them down.

The Sunset Shimmer of the Equestria Girls universe is a former agent of G.U.N.

• The Sunset of the EGs universe was a protégée of Principal Celestia similar to how Sunset from Equestria was Princess Celestia's apprentice. This Sunset got into an accident that left her crippled and forced to be placed in a life-support tube where Celestia visits her from time to time. Although some shady agents, including Robotnik, go behind her back and experiment on her; turning Sunset into a super soldier. The experiments cause Sunset to lose memory of her previous life and later team-up with Shadow; where they will then break out of the G.U.N. facility to find the truth.

Scootaloo's parents are G.U.N. agents

• Similar to their pony counterparts being explorers, Scootaloo's parents could have been GUN agents, which does explain why they don't live with Scootaloo (her aunts having custody of her) due to being busy with world traveling GUN missions.

Diamond Tiara has a crush on Apple Bloom

• In light of Volume I, Chapter 6 in the second movie having Apple Bloom being curious on if there's more to Diamond's friendliness with her beyond wanting to be The Atoner for her initial bulling of her, it is possible.

Guesses on who the mysterious figure with long hair watching Sonic in the second movie is

• Principal Celesta: Having been said to have gone off the grid after the events of the first movie, it is possible she could be spying on him for a potential plan to keep tabs on him and Sunset behind the scenes.
• Bon Bon: A nod to her pony counterpart being an undercover agent.

Other potential EGs characters showing up.

• Since the human counterparts of Tempest Shadow, Grubber, Rainbow Blaze, Lightning Dust, and the Washouts have shown up. There could be a number of other characters that will be introduced that have never shown up in Equestria Girls canon:
  • Autumn Blaze and the Kirin: They could be the inhabitants of Hoovai that will greet the Rainbooms and their classmates when they arrive.
    • Confirmed in Volume 1, Chapter 8.
  • Limestone and Marble Pie: Attending the graduation ceremony to see Pinkie graduate.
    • Confirmed in Volume 1, Chapter 7.
  • Cloudy Quartz, Igneous Rock, Hondo Flanks, Cookie Crumbles, and Fluttershy's parents: Also seeing their daughters graduating high school, with Hondo and Cookie also likely getting some scenes on how they punished Sweetie Belle for her part in the school fire.
    • Confirmed in Volume 1, Chapter 7.
  • The Young Six: They could possibly be students in the same grade as the CMC.

In addition to Princess Twilight attending the graduation ceremony, Equestria Spike and Starlight Glimmer will show up in the second movie.

• Considering the Continuity Cavalcade nature of the movies so far with the first one having every EG villain and character (except Wallflower Blush but she is mentioned and Ragamuffin), Equestria Spike and Starlight Glimmer visiting the human world to help out isn't too far fetched especially since Equestria Spike was shown to be associating with the Rainbooms in the first two EQ films and Starlight befriending Sunset in Mirror Magic.

Robotnik will steal Princess Celestia's magic.

• Since it's hinted that Princess Celestia will show up in the human world to witness Sunset's graduation, there's a chance she will meet Robotnik. When she sees how big a threat Robotnik is, she will try to take down the evil doctor, only for the Mad Scientist to use the Master Emerald's powers to drain her of her magic.

Sci-Twi was cloned from Robotnik

• Since it is mentioned that the human versions of Twilight Velvet and Night Light had found her as an infant and took her in from a horrible place, it could be possible G.U.N. had tried to make a gender swapped clone of either Dr. Robotnik or even his grandfather Gerald Robotnik because of their high intelligence, explaining a lot of Sci-Twi's own intelligence, and seeing it as useful to them in case the Robotniks turned against them.

The native human Sunset Shimmer was killed in a G.U.N. related accident

• In the epilogue for the first movie, it is mentioned Commander Walters had killed and swept others' deaths under the rug in the past, it is possible G.U.N. had killed human Sunset Shimmer and erased all evidence that she ever existed like they did with Robotnik between films (explaining why Robotnik was unable to find any records of a "Sunset Shimmer" from before the pony one arrived in the human world for the first time, not even from a potential human counterpart). Based on Principal Celestia and Walters' conversation in said chapter, it is possible human Sunset was Principal Celestia's adopted daughter with human Sunset's death being the reason for Principal Celestia's relationship with Commander Walters souring and her (as well as Vice Principal Luna and Dean Cadance) leaving G.U.N.

The Kirin work for G.U.N.

• Since the Kirin are at Hoovai where all the students of CHS are to have their graduation ceremony. Chances are that they have been assigned to work for the organisation to keep an eye on Sonic.

Cinch is a former member of G.U.N.

• Cinch's conversation with Stone at the end of the first movie and Cadence being revealed to also be a member of G.U.N implies that the former principal of Crystal Prep used to work for the organisation as well. Cinch may have been fired from the organisation due to partaking in illegal activity that may also involve something to do with Shadow as well as what might have happened to the human Sunset Shimmer.

The Young Six's roles in the human world.

• Gallus: A student at CHS, who is in the same grade as the CMC. Like his Equestrian counterpart, he's a Deadpan Snarker who is known for having a problem with authority. As a result, Gallus is almost always seen in detention, whether it is for starting a food fight or not doing his homework assignments. However, underneath the tough, snarky exterior lies a boy with severe abandonment issues due to growing up in the foster care system for an early part of his life before later being adopted by an old man named Grandpa Gruff. Regardless of his attitude, he does care about his friends a great deal, is willing to stick with them and take part in their shenanigans, no matter how dumb they are; if only to snark at them.
• Silverstream: A student at CHS, who is in the same grade as the CMC. Like her Equestrian counterpart, she's a Genki Girl who is always excited about learning new things and is a fond member of Canterlot High's Arts and Crafts club. She's into numerous artistic and creative activities such as drawing, painting, sculpting, etc; and is willing to show her talent to the world. Edith (who is a parrot in the human world) is her pet.
• Smolder:
  • A dog, who is Human!Ocellus pet.
  • A student at CHS, who is in the same grade as the CMC. Like her Equestrian counterpart, she's a Tomboy with a Girly Streak with her common interests being skateboarding, playing video games, reading comics, but also engages in girly activities. She enjoys coming to the animal shelter to look after the animals along with Fluttershy and is also fond of taking care of Spike. Her gamer name online is "Dragon Princess" and is shown to be a pro gamer capable of beating almost anybody, including Sunset. Sunset will be surprised to know that Smolder is the one who beat her games all the time.
• Ocellus: A student at CHS, who is in the same grade as the CMC. Like her Equestrian counterpart, she's a Shrinking Violet who has a tendency of fading into the background, but is also a Nice Girl who wishes to gain the courage to express herself and as a result, joins the CHS' cheerleading squad. She's a straight A student and is known for tutoring her friends for upcoming tests. However, a reason for why she's so shy is due to coming from a strict upbringing and wishes to not disappoint her parents. Dog!Smolder is her pet.
• Yona: A foreign exchange student at CHS from the human world equivalent of Yakyakistan and in the same grade as the CMC. Like her Equestrian counterpart, she is a clumsy Gentle Giant who reminisces about her old home and shows off artifacts from her culture. She is part of CHS' cheerleading squad, occasionally getting injured due to her clumsy tendencies but is always happy to help out. She's currently dating Sandbar. Spindle and her babies are her pet spiders. Also, unlike her bovine counterpart in Equestria, Human!Yona doesn't speak in third person.
• Sandbar: A student at CHS, who is in the same grade as the CMC. Like his Equestrian counterpart, he's pretty laidback and serves as the voice of reason in his group of friends whenever arguments erupt between them. Sandbar likes to keep up with the latest trends, whenever a cool gimmick or product is out there, he'll want to try out; most of the time he even brings his friends to join him on his activities. Despite his nonchalant attitude, Sandbar feels insecure around his friends as he sometimes feels like he's not special compared to them and has nothing new to provide to the table, showing that he has an inferiority complex. Sandbar likes swimming, going to the beach, and collecting seashells. He's currently dating Yona.