I just don't get my kid. He tells me he's trying to level up, but we're already on the top floor of the building, and he's just sitting in front of his game box.

BADA - BING, you been punned!

You see, it's funny because the parent doesn't get that the kid is trying to gain experience points in his video game, and related leveling up to climbing the stairs to the next floor of the building, but they are already on the top floor - so the parent is confused! Confused parents are funny!