The Magilla Gorilla Show (1964)

S1E6 Small Change

Mushmouse sneaks into the kitchen, hoping to grab a quick snack. However, when he swings open the icebox door, he finds Punkin’ Puss waiting for him. In an effort to match the cat's size, Mushmouse consults a spell book. Unfortunately, the spell backfires, causing Punkin’ Puss to shrink down to Mushmouse's size instead. Seizing the opportunity, Mushmouse plans to cause some mischief for his feline friend.