This is a bit tenuous, but it did involve my groin and I think it's funny, so:
Many years ago, staying at my boss’ house after a night on the booze with some customers. Creeping into the house so as not wake his sleeping wife, we bade our goodnights. His house was on three levels; my bedroom and bathroom was on the first floor, while his was on the second.

Creeping silently like a cat into the bathroom, I expertly knocked a metal beaker off the basin, then spent what seemed like ten minutes chasing it around the (fully tiled) bathroom, like I was trying to create the world’s first human-powered perpetual bell. Luckily, this didn’t seem to wake the whole of Docklands, so I brushed my teeth and went to bed.

The following morning I felt what can generally be described as “fucking awful”. The full works: headache, tongue like a mouldy carpet, pounding heart, trembling limbs, nausea, ringing in the ears, unsteadiness on the feet. There was only one thing for it: a shower! Everyone feels better after a shower, and my boss has a very nice house, the shower will be fab. Off I went to the bathroom. Glaring at the metal beaker, I stepped into the bath and luxuriated under the hot spray. Lovely, I do indeed feel better, this isn’t going to be such a bad mor…

…and then I stepped out of the bath, onto the mat.

I’ve already mentioned my trembling limbs and unsteadiness. The bathroom floor was a few inches lower than the bottom of the bath, which I wasn’t expecting. I shuffled my foot away from the bath to regain my balance, then a bit further away from the bath, and then a bit further.
You can probably see what’s coming; after all I already mentioned that the bathroom is fully tiled. My foot shuffled off the mat; all grip was lost and I did the splits. My left leg shot towards the door, my right leg stayed in the bath and I swear my nuts hit the floor. I ended up wide-eyed and gasping for breath, gripping onto the sink, not knowing whether to laugh or kill myself.
Eventually I managed to stand up and limp back to the bedroom, all healing effects of the shower thoroughly negated. It was a looooong day...

tl;dr – hangover causes slapstick moment, multiple pains ensue including one in the groin
(Professor Kenny Martin Hmm? What?, Fri 8 Mar 2013, 9:20, 2 replies)

It's not a sink
It's a basin.
(Bob the Builder killed Captain Alex, Mon 11 Mar 2013, 20:36, closed)

You're right, it is
And now I've edited it :)
(Professor Kenny Martin Hmm? What?, Tue 12 Mar 2013, 12:06, closed)