Having a quickie

A couple decided that the only way to have a quickie while their ten-year-old son was in the apartment was to send him out on the balcony and let him give a running report on what was going on in the neighborhood.

So the boy stood on the balcony and reported on everything that was happening...

"A police car has just called at the Hamilton's' house, the Chandlers are taking delivery of a new wardrobe, and the Mitchell's are having sex."

Hearing this, the boy's parents shot bolt upright. "How do you know the Mitchells are having sex?"

Spoiler:

"Because their kid is standing on the balcony too."