Other mistake: In the closed-captioning, when Arnold and Gerald "touch thumbs" (and you hear that "sproing" sound), the caption says "[glass shatters]"
Kingdom Come - S1-E6
Other mistake: At the start of chapter 12 in the episode "Kingdom Come," Frank returns home via taxi. In front of his house in Seattle, WA, there is a blonde woman walking a Rottweiler dog. This same blonde and Rottweiler can be seen walking by the crime scene in San Francisco in the "Gehenna" episode.
Other mistake: Lucy's drivers license says her birthday is in January but she was conceived on Valentine's Day.
Episode #1.3 - S1-E3
Other mistake: After the Demon Headmaster has been drenched in goo on the TV show Eddy Hair ends the show and there is a shot of the children shouting his catchphrase, in this shot you can see Eddy's cameraman crouched on the floor at the bottom of the stairs looking injured and holding his arm. There's no explanation as to why. (00:20:49)