Sheldon and Amy do a scientific evaluation when she gets turned on by Zach. They determine that she's horny. He wants her to go out with Zach, but instead she tries a hand-holding experiment with Sheldon.
Sheldon: Here's an interesting fact about alcohol ... Man is not the only species that ferments fruit in order to become intoxicated. Can you guess what the other is? Hint: sometimes they pack the alcohol in their trunks. Penny: Monkeys Sheldon: When does a monkey have a trunk? Penny: When a suitcase just won't do Much later - Sheldon: And the answer was elephant.