A man unable to perform in bed goes to see a hypnotist. The man is hypnotised and told if he says '1 2 3' he will get the mother of all hard ons for as long as he wants. The hypnotist warns though that if he says '1 2 3 4' he won't be able to get an erection for a year.
The man goes home, grabs his wife from behind, bends her over the table and shouts '1 2 3!' His wife shouts back 'what are you shouting 1 2 3 for?'