It's revealed in this episode that Amy attended college at Harvard and Leonard attended Princeton.
Amy reveals that her favorite TV show as a child was Little House on the Prairie.
Bernadette: Quitting would be the worst thing for your relationship.
Bernadette: Because it would make you seem like something she (Penny) already thinks you are.
Leonard: What does she think I am?
Bernadette: How do I put this? She's been known to call you a name that usually applies to a lady part. Or a cat. Or a willow.
Leonard: I can't believe she would say that about me.
Bernadette: If you're gonna cry about it there's tissues in my purse. Unless you got some in yours. Big willow.