As the guy drinks his first beer the monkey sits patiently on his shoulder. When he's finished the beer the guy smacks the monkey hard; smacks it so hard it falls to the floor. The monkey, a bit dazed, struggles to stand and climbs awkwardly up the guys leg.
When the monkey has climbed as high as the guy's trouser zipper, the monkey pulls down the zipper and performs, on the guy, what can only be described politely as an act of oral sex. When the job is complete... the monkey fastens the zipper and climbs back up to sit patiently on the guy's shoulder again.
By now an excited crowd has gathered. The latecomers missed the performance and want the guy to repeat it. Sure enough, the guy smacks the monkey; smacks it hard. Monkey falls to the ground, climbs the guy's leg, unzips the zipper, performs the 'act', fastens the zipper and climbs back onto the guys' shoulder.
Meanwhile, right at the back, in the corner of the bar, a little old lady has been watching. She gets unsteadily to her feet, and with the aid of a stick, hobbles over to the man with the monkey on his shoulder. 'That's amazing' she croaks. 'Can I have a go at that?'
'Sure' says the guy, 'sure you can have a go'. And as he begins to lift the monkey off his shoulder the old lady says 'Can I ask one thing though?' 'What is it?' asks the man.
'Don't hit me as hard as you hit that monkey.... '