Penny: Could you two really have some sort of super-intelligent child?
Amy: Well, there is a genetic component, but that doesn't guarantee anything.
Leonard: That's true. Sheldon's father once picked a fight with a cactus.
Penny: Yeah, but that's just his Earth parents. We don't know anything about the ones that sent him here.
Leonard: Well, we know they were smart enough to send him away.