I blame Rag Mags for this.
When I was a smallish wertperch, around fourteen or so, I'd found a Nottingham University Rag Mag. For those not in the know, these consist of old, bad-taste and disgusting joaks "edited" into a magazine and sold by students, allegedly to benefit charity.

Now most of the jokes were too foul to remember, but one of them was a delight of surreal humour, so I memorised it.

Some time later, I was at a dinner party thrown by my father (at the time an RAF officer), and decided, in a lull in the conversation, to tell the following:

Q: What's grey and comes in pints?
A: An elephant!

In the stunned silence that followed, I realised that Something Was Wrong in a Big Way. Thankfully, everyone put it down to childish misunderstanding, which it was, and no-one said anything to me. It was only much later that I finally understood the joke, and even now, I cringe as I recall this incident.
(wertperch is losing his hair, marbles and patience., Mon 16 May 2011, 3:01, 1 reply)

I first heard that one at 14 and had no idea what it meant.
Same with 'What's white and glides across the dance floor? Cum Dancing!'

I wouldn't have understood even if I'd seen them written down. Probably made it funnier for my friends, though. The bastards.
(Juan Quar is clinging to her front teeth on, Tue 17 May 2011, 7:24, closed)