Curious questions from curious kids

The first one comes from my four-year-old daughter, Ridley. We were reading "Eight Silly Monkeys".

Me: "Eight silly monkeys jumping on the bed, one fell off and bumped his head. Mama called the doctor and the doctor said, 'No more monkeys jumping on the bed.' "
Ridley: "How does the doctor know they were jumping on the bed?"
My question: How does a four-year-old come up with that?

Then, a couple days later I get this from my six-year-old son, Boston, after watching an old "Scooby Doo".
"How come Shaggy eats SO much but stays so skinny?"
My reply, "Good metabolism."
Boston was thoroughly confused.