Mr. Monk Gets Cabin Fever - S3-E12
Other mistake: When Stottlemeyer is about to eat his cake he is looking at Monk. Shortly before he starts to pick up a piece of cake you can see he is pretending to chew a piece in his mouth. Throughout the scene you can see Stottlemeyer's face and the cake. At no point before he pretends to chew does he put a piece in his mouth.