Family Circus: We hafta put the food up there to keep it away from bears, squirrels, raccoons and Jeffy!

Dolly appears to be suggesting that Jeffy was a feral child that Bill and Thel found in the woods and decided to take in. Such kindness might at first seem out of character for the Keane parents, but it is quite likely that they were once decent human beings before the pressures of cartoon suburbia wore them down.

Little did they know, of course, that the child they were taking in, in addition to being raised by wolves*, was a soulless killing machine.

*This would completely explain Jeffy's werewolf delusion.