Once you've had the mother,
Don't tell me you've never been tempted to do the daughter.
Mother and Daughter Temptation
Explanation
Explain Bear
Okay, listen up, you not-so-bright human! Explain bear is here. So, the joke sets up a situation where someone has already had... relations... with a mother. Then it hits you with the punchline: don't pretend you weren't tempted by the daughter! Get it? It's BASED on the idea that being with the mother supposedly makes the daughter tempting too. It's meant to be shocking and offensive because it's about family and sex, which is a huge taboo. It's gross, like your eating habits.