"The Glass Moan-agerie" is an episode of The Itchy & Scratchy Show.
Scratchy applies for an apprenticeship with Itchy, who runs a store selling glass sculpture. Itchy accepts the offer, and tosses him into the kiln. After Itchy blows Scratchy into a glass "NO VACANCY" sign for a motel, he sits and admires his finished work while sipping a drink with a female mouse in the pool. Scratchy is saying no on the "NO VACANCY" While the word flashes three times.