Sixth Ranger Traitors in Western Animation.
- Chip 'n Dale: Rescue Rangers:
- Foxglove helped the Rangers mainly so she could steal the episode's Plot Coupons they found, and give them to the villain/goons she worked for... and also because of an affection for Dale, which lead to her Heel–Face Turn back to the Rangers.
- Desiree D'Allure, Monterey Jack's old crush, does this as well... except unlike Foxglove, she stays evil, and gets away with it! (Well, not completely.)
- William from Code Lyoko joins the team in the second-to-last episode of the third season, even though he was already considered 7 episodes ago. Although he is not evil and never becomes evil, his inexperience and cockiness combined with some errors from the heroes themselves led to XANA taking him over in the following episode. The surprise factor was actually legitimate, because the build-up was so long.
- In G.I. Joe: Sigma 6, Firefly ends up betraying the team to Cobra.
- In the second season of The Legend of Korra Varrick is this for a while to the Krew. Even when he begins manipulating and betraying some of the members, it takes them a while to figure it out. Even after he's exposed, he still thinks they're friends. He does eventually do a Heel–Face Turn a good two books later, but he had to earn everyone's trust and forgiveness again because of said betrayal.
- Discord pulls this stunt in the Season 4 Finale of My Little Pony: Friendship Is Magic after listening to Tirek's Hannibal Lecture. Getting swiftly backstabbed, drained of his powers, and still forgiven by his former friends kicks him back to the pony's side for good... probably... hopefully... and with his actions in the final season, sort-of-but-not-really. At least the Distant Finale implies he finally got that "good" thing figured out.
- All groups of 6 heroes have one of these. The Pillars of Old Equestria has Stygian and the Young 6 have Cozy Glow. Stygian performed a Heel–Face Turn, while Cozy Glow... didn't.
- She-Ra and the Princesses of Power: In season 4, Double Trouble joins the Rebellion in disguise as a young girl named Flutterina, but is actually a Horde spy who's ruining missions and distracting the team while the Horde conquers Salineas.
- Star Wars: The Clone Wars: In the episodes Downfall of a Droid and Duel of the Droids, R2-D2 goes missing in battle. He is replaced by R3-S6, a bumbling droid who tries to do as commanded but can't seem to do anything. While Ahsoka gives R3-S6 the benefit of the doubt, believing the droid just needs time to master all the skills that R2-D2 was capable of, it's eventually revealed he is actually a malicious bot planted by General Grievous to spy on the Jedi and to actively thwart as many plans of action as possible.
- Steven Universe:
- In "Bismuth", the eponymous Gem joins the main group, and even shows up with the rest of the main cast in eyecatches. While the character isn't a traitor, they do turn out to be a Well-Intentioned Extremist who ends up fighting the main character Steven. Ironically, Bismuth views Steven's mother as having betrayed her, since Rose imprisoned her for crafting a weapon that can shatter gems... and failing to see the hypocrisy of turning Homeworld's most heinous tactic of intimidation against them. The character is re-imprisoned at the end of the episode. Two seasons later, in "Made of Honor", she comes back and permanently rejoins the team with no violent intentions.
- Another episode sees "Navy", a member of the Quirky Miniboss Squad of Rubies, say she wants to join the Crystal Gems. Garnet is hesitant, but Steven gives her a chance and has the team's actual sixth rangers, Peridot and Lapis, show her the ropes. However, Navy just wanted to take back her ship, which the Crystal Gems had previously commandeered and Peridot had been tinkering with. Once she, Steven, Peridot, and Lapis are on board, she takes off on a test flight, only to eject the heroes and escape.
- Terra from Teen Titans. Unlike in the comics, where Terra was Evil All Along, Terra started as an ally, rejected membership over a misunderstanding, and had become The Mole by the time she took it up. If it wasn't obvious enough that Terra as a Titan wasn't going to last long, the episode following her joining the team has her suspiciously absent save a very brief non-speaking cameo in the end, and the title of the next episode when she actually appears as a member of the team? "Betrayal"
- In Thunder Cats 2011, Pumyra is actually a Dead All Along Femme Fatale who wants Lion-O dead for accidentally abandoning her to die in the rubble of Thundera.
- Longarm Prime from Transformers: Animated is introduced in a flashback as Bumblebee and Bulkhead's loyal classmate in boot camp, but the end of the episode reveals him to be Shockwave in disguise.
- In Robotix, the Protectons eventually revive another of their frozen comrades into a robot body, but unknown to them, Nemesis switched things so the body actually houses the mind of one of his minions, Venturak.
