Yo Mama So Fat

Okay, so you're not smart. Here's the deal: this joke is based on hyperbole. The joke says that a person's mother is so big that when she walks by the television, she blocks the view for an extended period of time. The exaggeration is that she blocks it for so long that a viewer misses three full episodes of a TV show. It's a classic example of making fun of someone's size by stretching the truth way beyond reality.