"Wild Card" joke

One day, little Johnny came home from school. He went into the house and found no one around, which he thought was strange because his parent's car and his grandparent's car was in the driveway. So, he searches all over the house. Finaly he went up stairs to his parent's room and opened the door. There was Dad and Mom having sex.
"what are you doin, Dad?" little Johnny asked.
Playin' poker, son, and your mom's my wild card. Go find Grandpa and Grandma."
So off Johnny goes to the next bedroom and there are grandma and grandpa having sex.
"What are you doin' Grandpa?" little Johnny asked.
"Playin' poker and Grandma's my wild card".
So little Johnny leaves the room. A few hours go by and it's time for dinner, but nobody can find little Johnny. Dad goes up to Johnny's bedroom and finds him there masterbating.
"what are you doing?" Dad asks.
"Playin' poker, Dad," Johnny said.
"Well, where's your wild card?"
Little Johnny replies, "With a hand like this, I dont need a wild card!"