My apologies. One of my mates has been foisting it upon me at every opportunity for days, and I can't help enjoying it, and nor could I keep it to myself any longer.
A woman wakes up with a terrible hangover and finds herself sharing her bed with an elephant. "God I must have been tight last night!" she exclaims. "Yes," says the elephant, "at least the first couple of times."
Luckily I can't be bothered to type out the hamster joke.