gigantikok: Beeeee-zare, but I've read articles on this before. Most ads are usually just skimmed through in magazines, and that is not good enough for most advertising companies. They want to capture the reader's attention somehow. It has been tested and proven that if there is something just SLIGHTLY bizarre or "off" about an advertisement, the reader will have a higher chance of remembering it while skimming by (if not stoping altogether to examine the strange ad). And bingo, you've got yourself a potential customer. All it took was an extra leg.
(You see the "third leg" ad type often, but sometimes models have three arms and other variations.)