Transylvanian Homesick Blues - S2-E65
Character mistake: Ray says that it's the very first time they've dealt with vampires. In Season 2 Episode 25, "No One Comes to Lupusville", the Ghostbusters had to deal with both werewolves and vampires.
Yomigaere! Eiyuu Densetsu - S1-E1
Character mistake: Not to dispute physics in an anime about people drawing arcane cosmic powers from constellations, but when Marin explains to Seiya what happens when you shatter a rock into smaller pebbles, she says that you "destroy its atoms." That's not how physics works and luckily for her, Seiya and everyone else in Greece at the time, she did not create a nuclear fission in the palm of her hand just to prove her point.