Das Subway / Wheezin' Ed - S1-E12
Factual error: There's no way Grandma could have connected two "live" wires with her bare hands without electrocuting herself, and there's certainly no way the wires could have stayed connected.
Helping Hands, Iron Fist - S1-E4
Factual error: When Bruce Banner sees the Hollywood sign reflected in the puddle of water, the reflection is backwards.
Rangers of Two Worlds: Part II - S1-E47
Factual error: The climax of the episode features the Aquitain and Zeo Rangers fighting together, in Angel Grove. However, they are actually fighting outside the Tokyo Dome, in Japan. Further proof: http://www.rangergallery.com/albums/userpics/10012/Zeo%2520Rangers%2520and%2520Alien%2520Rangers.jpg.
Double Dose - S2-E10
Factual error: Season 2 episode 10 "Double Dose": When Superman snatches Parasite's escape boat and hauls it back to Stryker's, Parasite attempts to blast him with a shotgun found aboard. But somehow the animators appeared unable to decide whether the gun should be a double-barrel or a pump-action type; its type switches from one scene segment to another.