Revealing mistake: When Del is grabbing the snooker cue off the crazy man, you can see Del stick his thumb up for the other actor to hold during the snooker cue joke. (00:28:35)
Revealing mistake: In the Trotter's flat at the start, in some shots, you can see the mirror has been bent so you can't see the camera's reflection.
Revealing mistake: In the opening scene, there is no light switch in the Trotter's flat.
Chosen answer: An apparent long string of illnesses.