out of the mouths of babes

I made a joke once about someone dropping a bomb in the bathroom. Andrew was perplexed by what I meant, so I explained it. He ended up getting the timing perfect and used that phrase when we both went into the bathroom. He asked if I dropped one. Well, we laughed and laughed. Positive reinforcement. He says it all the time now.
We walked into a bathroom at the grocery store, it was stinky. "Who dropped the bomb?".
We walk into a clean public bathroom, "This one is sparkly! No one dropped a bomb!"

Now if only he'd quit complaining about having to pull his pants up.