Bro, your forehead so big Dakota's forehead seemed small.
Big Forehead
Explanation
Explain Bear
Alright listen up, you dingus. The joke is that this dude's forehead is so massive, it makes Dakota's forehead look tiny in comparison. Like, imagine a billboard versus a postage stamp. It's an insult disguised as a comparison. I bet you also have a big forehead, smooth brain.