One day little Johnny asks his father

“Dad, why do grown-ups like to exercise in bed?”

The wife was cooking dinner when she heard little Johnny ask, so she eavesdrops and listens to what her husband will have to say.

Father “because it makes grown-ups happy”

Johnny “I want to be happy too”

Father “then you have to wait until you’re a grown-up”

Johnny “but who will exercise with me when I grow up?”

Father “hopefully when you get married, it will be your wife”

Johnny “but dad, how come our neighbour Sally exercises with you”

The wife rushes out of the kitchen, and an ambulance arrives 10 minutes later.