The Dirty Grandma Joke

There once was a little boy who was celebrating his 11th birthday.

He decided to test his family to see if they remembered his birthday, so he goes downstairs to his father. "Bet cha' can't guess how old I am today", the boy said.

The father has no clue and finally gives up. "I'm eleven!" the boy exclaims.

Next he goes in the kitchen, walks up to his grandma, and says, "Bet cha' can't guess how old I am today".

"Let me give it a guess", grandma says and sticks her hand in his trousers.

She plays with his testicles for about an hour or so (squeezing them; moving them back and forth), takes her hand out of his trousers, and says, "You're eleven years old".

"How did you know?" the boy asked.

Grandma replied, "I heard you tell your father".