Yo mama's so fat, a man has to bring climbing equipment to kiss her on the cheek.
Climbing Equipment
Explanation
Explain Bear
Okay, listen up, genius. This "yo mama" joke is all about exaggerating how fat someone's mama is. Like, she's so big, a dude needs climbing gear just to plant a smooch on her cheek. It's funny because it's so over-the-top, and probably because you're not very bright.