I'm not clued up on BBCode these days, so if you, by chance, are under the age of 16 or have a sensitive disposition with regards to 9/11, I advise you to skip this post.
A father and son, on a trip through their local nature preserve, notice a couple engaged in sexual intercourse, through the tree line. The son, perplexed, questions his father on those people were doing. Quickly, he responds, "Ah, you see, they're baking cakes." The child nods and the two carry on down the trail. Some time later, the boy spots another couple having sex in the forest. He announces to his father, "Look Dad! They're baking cakes too!". The father nods and replies with a curt, "Mhm". They then begin to head home.
The next morning, the boy says his to his parents at the dinner table, that his parents were baking cakes last night in their room. His mother stares questioningly, the father panics and asks, "How did you know?"
"I ate the icing on the pillows, Dad."
Bonus joke: