Episode #1.2 - S1-E2
Revealing mistake: Towards the end of the episode when Dinah, Lloyd and Harvey are walking to school you can see a man and a woman stood at the end of their driveway watching filming. (00:19:28)
Episode #1.1 - S1-E1
Visible crew/equipment: When Lloyd and Harvey are studying in the library (just before Harvey says "what do you think they're doing?") the boom microphone drops down into the frame above Lloyd's head. (00:14:17)
Episode #1.1 - S1-E1
Visible crew/equipment: When we see Dinah, Lloyd and Harvey walking to school the first time if you watch the top of the screen you can see the boom mic drop down into the shot a few times. (00:04:42)
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)