This joke requires you to <insert friend's name here>. <Insert friend's name here> is walking along a country path and comes upon Mark Wahlberg enjoying some coitus with an unfortunate sheep whose head has become stuck in a fence. <Insert friend's name here> says, "Hey Marky-Mark, what are you doing to that sheep?" Mark replies, "I was just walking along this path and I saw this sheep with its head stuck in the fence, so I thought I'd have a bit a fun. Care to have a go yourself?" <Insert friend's name here> says, "I'd love to" and sticks his head in the fence.