Some characters in Happy Tree Friends are prone to "flipping" errors, such as Russell the otter's hook hand/eye patch, Nutty's lazy eye and Lumpy's inverted antler, which change from side to side even within the same scene. They also tend to give Toothy the "normal" buck teeth the other characters have instead of his trademark huge, gapped ones.
In one scene in "Flippin' Burgers", they managed to attach Cuddles' arms to his cheeksfor two seconds.
In Sniffles' first appearance, "Crazy Antics", during the opening sequence when he pops out of the bush, the bush disappears.
The Homestar Runner animation "In Search of the Yello Dello" is definitely full of this, especially with both Homestar and Coach Z's designs. The in-character commentary track for the cartoon indulges in a little Self-Deprecation:
Strong Bad: Little known fact, Homestar gained a hundred pounds and shrank two feet for this role. Homestar Runner: It's true!
Powered By The Cheat toons tend to be off model as well, though this is due to Stylistic Suck.
Quasi-intentional in a few episodes of Extra Credits: occasionally Allison Theus (the main artist) is unavailable that week, and they get another artist to draw it, who will usually have an entirely different style.
Due to the simplistic art style in DSBT InsaniT and Dreamscape, this is bound to happen, mainly by the character's arm movements.
The BIONICLE web-game Mata Nui On-Line Game infamously mixed up the character models for Hafu and Taipu, whose sole differentiating feature is their masks — Hafu is supposed to have a Ruru, and Taipu a Pakari. Strangely, Kapura (who wears a Ruru according to his promo pic) also got a Pakari for the game. The sequel pokes fun at this, having the player character confuse Hafu and Taipu (now wearing the correct masks), who respond by angrily asking why people keep mixing them up.
The design of the Pakari mask also kept changing — it's close to the real thing at first, but from the middle of the game, it's stuck in a very off-model design, becoming on-model only in the second "episode" of the Flash animation series that takes place after the game.
Toa Gali has these short "rods" sticking out of her thighs, but only Pohatu is supposed to have those.
After the final minigame, there's a scene of the villagers discussing their victory, and one of them, Matoro, has a crude sketch for a mask that turns normal if you click on him and he faces you.
Eye colors are often inconsistent throughout the animations.
In the on-line animation for the Vahki Zadakh, the design of their staffs (Staff of Suggestion) changes to the type carried by the Vahki Nuurakh (Staff of Command), when the Zadakh are shown from afar.
Toa Hewkii in the non-canon 2006 animations (done by a different team) is brown colored, even though his toy is gunmetal gray.
The appearance of several characters in the Voya Nui On-Line Game greatly differs from their toys', having been modeled after their prototypes rather than the finalized designs.