Context clues

Kid 1: I saved these animals from a thorn bush!
Me: They must be thrilled.
Kid 1: No, they're nice animals.

Still Wilbur

Kid 2: You're the daddy monster... And you're the mama monster... And I'm the baby monster!
Kid 1: And I'm the family pig!

Jocularity

Kid 1: Mom, wanna hear a joke? What if... someone put their face first in YOGURT?

She's got the "funny" concept but not the part about the punch line.