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Photo credit: YouTube, Dan Giller – Kids join David Letterman to tell jokes.

Family, Kids, Popular

It took 3 minutes for a child to tell David Letterman a ‘knock knock’ joke but it totally delivers

Cecily Knobler

7/31/2025
An Operation Smile volunteer reverses an oxygen mask so a child with a cleft condition can blow a bubble for the first time in Guadalajara, Mexico. (Operation Smile Photos)

In Partnership With Operation Smile →

Family, Science

How Bubbles Help Kids with Cleft Conditions

Sarah Watts

5/11/2026