On their wedding night, Bruce displays his member to his new virgin bride and tells her it's the only one in the world.

She, of course, believes him. He's gone to a conference for a couple of weeks. He returns, only to be questioned by his new wife. 'Bruce,' she says, 'I thought you said you had the only one in the world. But Harry at the drug store has one too.'

'Well, er,' Bruce flusters, 'Harry and I were in the war together, I had two, so I gave him one of mine.'

'Oh. Well, why did you give him the best one?'