Madonna and Lady Gaga: two shameless pop stars willing to try anything, no matter how abominable or shocking , to secure a seat at the top of the charts (and tabloids). Some say that Lady Gaga is merely a Madonna clone, while others sing her praises as a fashionista and a perfect example of a woman who refuses to be defined by anyone but herself. Whichever way you look at it, Madonna and Lady Gaga have gone through more phases and costume changes than most of us have hot dinners. We revisit some of the most memorable.