Trevor has had a few drinks and goes to a restaurant to eat. After a while, he needs to break wind. The music is quite loud, so he times each fart with the beat of the music.
Soon he starts to feel better, and calls the waiter over to order coffee, only he notices everyone staring at him.
The waiter looks at him and mimes pulling a pair of earphones from his ears.
Then it dawns on Trevor...He's been listening to his iPod all along!