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.
Moero! Pegasus Ryuseiken - S1-E2
Other mistake: In the ending shot of the tournament bracket showing the potential future opponents, the two saints' names are written the wrong way, as "DORAGON" and "ANDOROMEDA", instead of Dragon and Andromeda. (00:22:00)