Girl Trouble / School Dance - S3-E18
Continuity mistake: Besides the fact that when Helga is sharpening her pencil, the desk arrangement changes, one of the students visible when she looks at Arnold is... Helga. This happens because the shot is taken from the episode "Helga's Love Potion."
Darkness and Light: Part 1 - S1-E11
Plot hole: When Hulk and Banner have been physically separated by the nutrient bath, they are both wearing tattered pants. Given that Hulk and Banner were previously occupying the same body, this should not be possible. Hulk was the one that went into the nutrient bath, so if Banner's body was separated from Hulk, then Banner should be naked.
Suggested correction: It was done deliberately as a form of censorship. They didn't want to show Bruce's genitals.
Explaining why the mistake occurred doesn't invalidate it. Unless you're suggesting the nutrient bath also was able to duplicate the pants.
You realise a character can be drawn naked without actually showing their genitals (and/or breasts in the case of women), right? The Little Mermaid is a good example of this.
Continuity mistake: The six Rangers are standing together as Wolfbane is enlarged by Orbis. Kat and Tanya change places when switching from the wide shot, to a closeup of the Rangers.
Deliberate mistake: Season 2, episode 6 "Identity Crisis": When Bizarro starts decaying into the parody form of Superman, his costume goes with it; the blue fades, and even the 'S' insignia changes. Strange that superhero garments change right alongside their wearers when they suffer from an unstable genetic effect. Were the clothes cloned right onto his body, instead of sewn?