How to Ruin a Joke

My mom’s favorite joke, played on some radio station.

ORIGINAL JOKE:
Johnny- Mother, can I have another piece of cake?
Mother- Yes, you may have more cake, but if you do, you’ll explode!
Well, Johnny ate another piece of cake and sure enough, he exploded.

RIDDLE:
What sits next to mother, eats cake and explodes?
Give up? JOHNNY!

FORGET PUNCHLINE:
You- Johnny asks mother if he can have another piece of cake. Mother says yes, but if you do, you’ll explode.So then Johnny er… Johnny um Johnnyyyyyyyyyyyyyyyy erm listens to mother?