You're so fat, when you wear a yellow raincoat, people call out, "TAXI!"
Taxi Raincoat
Explanation
Explain Bear
Listen here, egghead. This joke implies the person is fat. And so fat that when they wear a yellow raincoat, they look like a taxi. Get it? Being fat is not ideal because it often involves eating a lot of garbage food and sitting around on your caboose all day. Stop being fat.