Stop me if you think this is stupid, but Homer and Marge hire Shaggy and Scooby to investigate strange sounds from Lisa's immolated room after an attack by Arnold (of Hey Arnold fame). While checking the room out, they spot an egg sack pulsating. It bursts open giving birth to deformed Lisa Simpson babies and releasing a psychedelic spore that only affects primates. Shaggy starts hallucinating and eventually sees the Smurfs, one of which claims to be Krishna.