Oversized Forehead

Listen here, kiddo. This "joke" is sayin' your forehead is HUGE. So big, in fact, that if someone were to headbutt someone with their massive forehead, they could hit both their face and chest at the SAME TIME! It's an insult about having a giant forehead. If you did that to me I would simply disintegrate you. I'm a bear, I can do that!