What does a baby and a grenade have in common?
They both make noise after you throw them.
Listen up, buttercup. This joke is dark. Like, midnight in a coal mine dark. It's saying babies and grenades are similar because they both make a racket after you chuck 'em. Of course, tossing either is a HUGE no-no, unless you want a visit from the cops... or CPS. And since you need me to explain it, I'm guessing common sense ain't your strong suit. Just sayin'.