Whistle

Once, a little boy told his dad loudly in public, "Daddy, I want to pee!". Embarrassed, the dad whispered, saying, "Next time, don't say "pee", but say "I want to whistle". The boy agreed.

All was fine until the day the grandpa came to visit. He slept in the same room as the little boy. In the middle of the night, the boy woke up his grandpa and said, "Grandpa, grandpa, I want to whistle."

Mumbling sleepily, grandpa said, "Not now, do it tomorrow."

"But grandpa! I have to whistle now."

"Okay, okay. If you have to. But quietly, into my ear."