I recently picked up a copy of "Cards Against Humanity." My five and a half year old son saw it on the table and asked about it. I explained, "It's card game for grown-ups with themes you're too young for. By the time you're old enough to play it, you'll probably want to play it with your friends and not your parents."
"OK Daddy," he said, before moving on to something else.
The next morning I took him to school. He and a classmate charged into the room to grab a pack of playing cards with dinosaurs on them. This is apparently their favorite thing to pay with together. My son said to his friend, "Since people are made of meat, these are cards that eat Humanity!"
He then looked at me with a big, goofy grin on his face and I replied, while chuckling, "Good one. Well played son, well played."