Trivia: Fran's last name is Katzenjammer, which is German for "A momentarily severe hangover". It translates literally as "cat misery".
Trivia: The 'I Love Books' customer, seen at the beginning of 'Manny's First Day' is in fact, co- writer of the show Graham Linehan.
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.