Alvin and the Chipmunks (1983)

S1E22 A Dog's Best Friend is His Chipmunk

Alvin contributes funds to an animal charity, only to find out that the organization is broke. To raise some cash, they decide to sell the cookies that Theodore had bought with their money. However, when the Chipmunks stumble upon a dog, they realize they need to keep it a secret from Dave.