Continuity mistake: Bernard's accordion in certain shots is already damaged from when he kicked it in earlier takes, and other times undamaged until he kicks it.
Continuity mistake: When Manny is in the bath he wipes his hands dry before handling the toast, in the next shot his hands are covered in bubbles again.
Continuity mistake: In the scene where Bernard is trying to convince Manny he is insane, cornflakes suddenly appear stuck to Manny's dressing between shots. This is due to a short gag which was cut. (00:13:20)
Chosen answer: You may be thinking of S3E1, "Manny Come Home", when Manny quits and gets a job at Goliath Books next door. The device they use to scan books, look up items, or even order muffins is referred to as the "Doo-Deedee-Doo," after the sound it makes when employees scan their cards in it.