I did the same thing a few years ago, and called myself a Shark Cage Tester. Walmart was selling shark costumes for dogs for under ten bucks, and the small one fit on my leg perfectly. The large one, of course went on my parents' dog.

I've now done Oscar Pistorius (complete with gun to shoot into my bathroom in the dark), Lt. Shan instead of Lt. Dan, and the obvious pirate mixed with CAT5 cables to make an internet pirate. This year, I'm going as Leg-o-less, but it was a close race between that and problematic tramp, author, and poet W. H. Davies, since both of used to ride freight.