Another perennial favorite: Scooby Doo and his Scooby Snacks. But everyone knows that.

Some others that popped into my head later:

Pacman - Just keeps on popping those little white pills all right. And the powerpills? PCP.

The Cocoa Puff bird. "I'm cuckoo for Cocoa Puffs!" Well sure, get someone hooked on coke and all those dopamine receptors just cry out for more.