Fat Man in Nagasaki

Okay, you smooth-brained chucklehead, listen up. You clearly don't get it so let me explain it to you. First, this is a morbid joke so the punchline is related to death and horrible stuff. You think this is funny? Okay, second, Nagasaki is a place in Japan where the US dropped an atomic bomb in WWII. It's really awful. Lastly, the fat man is a reference to the bomb nicknamed "Fat Man". So instead of speaking, he explodes like a bomb. It's dark humor, you get it, right?