Best comeback

Not that this is a comeback, but..

One weekend evening, myself and a friend of mine (we'll call him John) were driving out in the country, passing through miles of farmland. We spot a sheep with its head stuck in a fence, and I say to him "Hey, I've heard that having sex with a sheep is actually quite like having sex with a woman." So we decided to give it a try. I let him go first. All the while, I'm very impatient. I keep tugging on his sleeve, saying "Come on John, let me go." He says "Hang on a second." But I insisted. "Come on, it's my turn!"
"Just wait a second!" He says
So finally he finishes, steps away from the sheep. So I stick my head in the fence..