The babies are munching on watermelon when Grandpa Lou walks by them. Grandpa Lou slaps Chuckie's back. He warns them not to eat any of the seeds, claiming they'll have a watermelon grow in their stomach if they do. Grandpa Lou gently pats Chuckie's back as he tells them this. Chuckie swallows a mouthful of watermelon and looks horrified.

Later, Chuckie tells his friends that he swallowed a seed. They worry Chuckie is going to explode because of this since watermelon is so big and Chuckie is small. The solution: to go inside Chuckie and retrieve the seed.

The babies plus Angelica try to shrink themselves using a light and it appears they are successful and go inside Chuckie in search of the seed. They travel the blood stream and pass through Chuckie's heart before finding his (lunchbox) stomach. Here it's revealed that Angelica actually wanted to ensure the watermelon would grow inside Chuckie and waters it. The seed sprouts and rapidly grows. Angelica is happy about it, until Tommy points out Angelica is still inside Chuckie and he'll explode with her and the babies inside. She never realized that and they flee Chuckie's stomach just as the watermelon grows large enough to make it explode!

Chuckie, curled up asleep on Tommy's floor, twitches, burps and the seed pops out of his mouth. Chuckie is happy and says they succeeded after all. Tommy says they haven't actually gone inside him yet: they only turned on the shrink light a moment ago.

Spike comes along and licks up the seed, but they probably won't try again.