I came across this picture on the web some years ago and filed it away. Having found it again, I did a search for 'Three Legged Stripper' and found the link. Apparently, the dancer goes by the stage name of 'Cloudy Day'. Her third leg is real and results from her having a parasitic twin. There are other better known and more marked instances of this condition. Rudy Santos is the longest surviving such case and more recently there is the case of Lakshmi Tatma. Lakshmi has gone on to have her parasitic twin removed. She was twice the subject of a British television programme on Channel 4 - before and after surgery. More details images of this procedure can be found at the Daily Mail.
I don't know what your immediate reaction to 'Cloudy Day' might be. One of my first thoughts was to wonder whether the extra leg was a left or right one. The developing embryo only makes left and right legs - there is no genetic information that produces 'middle legs'. I once saw the skeleton of a sheep which had an extra leg. It even had a rudimentary ball-and-socket joint at the mid-point of the front of its pelvis (the symphysis pubis) As you can see, Cloudy Day's has an extra right leg.