Yo mama so fat, she broke Usain Bolt's 100 meter speed record by taking ONE STEP!
Yo Mama Beat Usain Bolt
Explanation
Explain Bear
Listen up, buttercup. This joke is about your mom being so obese that just one step of her can beat Usain Bolt in a 100-meter dash. Usain Bolt is like, a super fast runner. You probably don't know him because you're too busy eating crayons.