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.