The Royle Family (1998)

The Royle Family at Christmas - S3-E7

Revealing mistake: When Barbera is shouting at Jim for winning £100 and not sharing it, Cadging Carol starts slicing cake with her spoon, but you can see there is no cake there.

Norma Speakman: Is this hat too far forward?
Jim Royle: No, we can still see your face.