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.
Factual error: Megatron tells Ravage that the Golden Disc was launched aboard the Voyager spacecraft, just as the Great War between Autobots and Decepticons began. Either Megatron is wrong or Cybertonian history is wrong, because Voyager was launched in 1977, and the Great War didn't begin until 1984 (the first season of The Transformers), seven years later. The disc can be read by lasers, but it was in fact an analog recording (as digital recording did not exist until the early 1980s with the compact disc). Just as well, the disc was only twelve inches wide; it looks much bigger in Beast Wars.
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; and building a double-barrel pump gun would be impractical due to additional weight and bulk.