A couple were sitting up waiting for their 15 year old son to come home from a social engagement when the boy came into the house with a big smile on his face.
"Hi, Mom! Hi, Dad!" he said breathlessly. "Guess what! I've just had sex for the first time, and it was wonderful!" His mother turned red and said to her husband, "He's your son. You talk to him." Then she left the room.
The father said "Son, that's great. Now you've become a man and I'm proud of you. I'm going to celebrate the occasion by buying you that ten-speed bike you've been wanting. I hope you don't mind waiting till payday to get it."
"That's OK, Dad", said the boy. "I couldn't ride it right now anyway. My ass is too sore."