There were a girl and a boy at the beach.

The boy looked at the girl and said,
"If you show me yours I'll show you mine."
...Later on that day, the boy is at home and walks up to his dad curiously asking
"Dad, what is this?" Pointing to his penis.
His dad replies,
"Son, that is your car, you want to put it in as many garages as you can."

The girl does the same thing but instead, walks up to her mom and points to her vagina and asks,
"Mom what is this?"
The mother says back, "Hun, that is your garage, you want to keep as many cars out of it as you can."

The next day, the boy and girl meet each other on the beach again, and as before, the boy says,
"If you show me yours I'll show you mine."

About 10 minutes afterward the girl arrives at home with a bloody face and her mother starts to become frantic, yelling in fear asking her daughter,
"OH MY GOD WHAT HAPPENED, WHAT HAPPENED?!?!"

The girl softly replies,
"Well mom, some boy tried to put his car in my garage, so I bit his left wheel off."

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Hope you enjoyed it! :)
Cheers.