Revealing mistake: When Mork rollerskates into the wall, the wall moves slightly.
Revealing mistake: When Pete asks Trev and Ted to look after the pizza place so he can take his daughter to hospital, Ted goes outside to speak to Chrissie. You can see a woman and a little girl in a pink dress walk past - the little girl has obviously seen the film crew and can be heard asking her mum "are we on the telly mummy?"