Ascended Fanon: The fandom gave Paulina the surname "Sanchez" despite her not being given a last name in the show, but it was made canon when Butch Hartman himself referred to her as Paulina Sanchez in a YouTube video.
Banned Episode: Due to Values Dissonance in the United Kingdom relating to the word "spaz" used in these episodes, "The Fenton Menace" and "Double Cross My Heart" are unavailable on Paramount+ in the country, though they're readily available to download on Amazon Prime Video there.
The Character Ice Cream Bar: Danny (in his ghost form) had a blue raspberry, strawberry, and lemon ice of his face, with green gumball eyes. The ice cream has been discontinued.
Children Voicing Children: Youngblood was voiced by Taylor Lautner when he was still a kid. Danielle was also voiced by child voice actresses, AnnaSophia Robb and Krista Swan.
Creator Couple: William Baldwin and Chynna Phillips, who voice Johnny 13 and Kitty respectively, are married in real life.
Cross-Dressing Voices: It was initially played straight for the nerd Mikey, who was voiced by Colleen O'Shaughnessey in his early, minor appearances. Subverted later on when he's voiced by Dee Bradley Baker.
Dawson Casting: Team Phantom were all voiced by adults. Even the youngest actor (Ricky D'Shon Collins, the voice of Tucker) was about 21 when the show first aired.
Development Gag: Johnny 13's motorcycle is a possible nod to Danny originally having a Cool Bike of his own early in development (Danny even rides Johnny's bike at one point in the episode "Livin' Large"). In one scene, Danny nicknames Johnny's shadow "Spooky," which could be a reference to how Danny was originally going to have a pet owl with that name.
Executive Meddling: A positive example: it was the higher ups who suggested that Hartman give Danny a logo.
Flip-Flop of God: So "ghosts" are really just monsters from another dimension who happen to use ectoplasm? Okay, but what about the countless references to ghosts being dead or previously being alive? Or, say, the Dairy King? Butch's answer to the latter is that ghosts with human backstories create said backstories for themselves because they want to be human. This might have been his original intent, but it's clear the vast majority of writers had different ideas.
God Never Said That: It's commonly stated that someone on the show's creative team, or even Butch Hartman himself, had confirmed Ember's backstory as her being an unpopular high schooler who wanted to be a rock star. One day, a popular boy asked her to the movies, but he never turned up; Ember ended up staying up all night waiting for him, which resulted in her sleeping through the freak fire that spread through her home and killed her. This fan-cited backstory has never been sourced. Not only does it contradict both Ember's Villain Song "Remember" (which implies that Ember died at least two weeks after the interaction) and Hartman's official stance that the ghosts in Danny Phantom are their own species and not the echoes of dead humans, it also doesn't make much sense on its own either. Why was there a fire, and why does Ember care so much about it if it was random? Why wouldn't anybody attempt to wake her up? Also, being awake for so long doesn't suddenly mean you have hypersomnia the next time you fall asleep.
The Lunch Lady is voiced by Patricia Heaton in the pilot episode, and Kath Soucie in her later appearances.
Mathew St. Patrick voiced Skulker in three episodes, before being replaced by Kevin Michael Richardson for the remainder of the series.
Speaking of Kevin Michael Richardson, he was the original voice for Dora in her dragon form before they switched to Susanne Blakeslee who also replaced Grey Delisle as her non-dragon voice.
While on the subject of Grey DeLisle, she started off as the original voices for Valerie and Star before being replaced by Cree Summer and Tara Strong respectively.
Valerie was also voiced by Colleen O'Shaughnessey in "My Brother's Keeper", the episode right before "Shades of Grey" which was when Cree Summer took over the role for the remainder of the series.
Also, Dani's voice actress switches from AnnaSophia Robb in "Kindred Spirits" to Krista Swan in "D-Stabilized".
Most of the voice actors in the Russian dub, except for Danny, Sam and Tucker, have been changed in season 3.
"The Fenton Menace" and "Identity Crisis" aired after "The Ultimate Enemy" but were set beforehand.
Despite being set afterwards, "Double Cross My Heart" and "Kindred Spirts" aired before "Reality Trip".
In addition, "Urban Jungle" was the first episode of the third season to premiere, even though it was number six. The Season 3 premiere didn't even air in the U.S until after the following seven. Honestly, Nickelodeon didn't handle new episodes very well.
The DVD sets place the episodes in production order. This isn't really a problem for Seasons 1 and 3 (in the latter's case, it even puts "Urban Jungle" in it's intended spot), but it is for Season 2 as certain episodes that took place earlier that season were produced later such as "Memory Blanked" which was the season premiere (and the episode where Danny gets his logo) but the sixth episode produced that season.
Real-Life Relative: Johnny 13 and Kitty's voice actors (William Baldwin and Chynna Phillips) are married.
Referenced by...: Some of the ghostbusting equipment in Ghostbusters (2016) strongly resembles the Fentons'. The Ghost Chipper works the same way as the Ecto Converter from the Danny Phantom episode "Secret Weapons" (the difference being Holtzmann's is intended to shred ghosts, while for the Fentons, it was an irrelevant side-effect). The Proton Glove is essentially (one of) the Ghost Gloves introduced in "Splitting Images." Martin Heiss also refers to the (now cylindrical) Ghost Trap as a "thermos."
Screwed by the Network: The show's ratings plummeted when the series went this route later in its run, with the third and final season's erratic schedule being a nightmare. The network cancelled the series in 2006.
Whatever the reason, Steve Marmel was no longer involved with the series after season 2. His plans for season 3 were never used or revealed.
Star-Making Role: While David Kaufman has had a pretty decent list of roles before Danny Phantom, such as Jimmy Olsen and Dexter Douglas, chances are most people will know him for his role as Danny.
Trolling Creator: Butch's regular discussion of ideas on how to revive Danny Phantom can come across as this, considering that he has no power over such a decision.
The Ghost Zone has a Heaven equivalent in the Elsewhereness and a Hell equivalent in the Unworld.
A few related to Ember:
She may secretly be in love with Danny, either currently or in the future, and hides it by acting the way she does. Speaking of the future, she even has his symbol on the side of her head (either shaved or tattooed). Her guitar is even shaped like the symbol!
As mentioned down below, she's supposed to be in her twenties but acts, looks, and sounds like a teen.
As mentioned above, Danielle was going to be adopted by the Fentons and become a little sister to Danny and Jazz.
The ghosts with human backstories (Desiree, Poindexter, the Dairy King, etc.) create said backstories for themselves because they want to be human.
Writer Conflicts with Canon:Post-series, Hartman retconned ghosts into a ghost-like species that takes the appearance of deceased people and makes human backstories for themselves. This is despite a large amount of Danny's Rogues Gallery having detailed backstories of once being mortal, with a few even directly mentioning their past lives.
Word of God is that Ember is in her twenties. She's called a "teenager" in her debut episode.
Random bits:
According to this Butch Hartman video, the lyrics and visuals for the first (unaired) version of the theme song were rather different than those of the final product. What's not mentioned is that the music that plays over the show's credits is an instrumental of the first version.
The name "Vlad Plasmius" was claimed by Marmel to be written on a brick he bought.
Tucker Foley was named after Chris Tucker and Eddie Murphy's character Axel Foley from Beverly Hills Cop. Jazz was named after a character from the Next Men series. Vlad is derived from Vlad Dracula III, the original inspiration for Dracula.
Because of the original intention for him, "Plasmius" comes from "plasma," or blood.
Danny Phantom's eyebrows were at one time (in production) white like his hair, but they were changed back to black—they made him look too old.
Look at Sam's room right after the theme song in "Control Freaks." Sam has a (musical) keyboard lying on her floor. Perhaps she plays!
Also, there's a red version of Ember's guitar in Jazz's room in "Fanning the Flames".
In a first season episode, where Tucker is editing his grades, the only ones he has A's in are Computers and ...Sewing.
According to one of the admins on Butch Hartman's forums (before the site eventually ended), Hartman stated not everyone can become a half ghost the same way Danny and Vlad did. Meaning if it were Sam or Tucker who entered the portal, it would have more likely killed them than turn them half ghost.
The show's/Danny's constantly noted resemblance to Spider-Man is hardly surprising once you learn one of the writers, Marty Isenberg, wrote 6 episodes of Spider-Man: The Animated Series.
Butch Hartman was heavily inspired by Jonny Quest in making the show.
Amity Park was named after The Amityville Horror (1979) as well as Amity Island because the show's creators wanted a scary-sounding name for the town, as the show revolved around ghosts and/or monsters.
, not only did Butch approve of it, but he also designed and voiced the "Rebreather" ghost used for a depiction of the average fight scene in the show.