It was the backhanded jab heard around the world. After years of mildly defending her most famous and obvious copycat, Madonna finally seemed to admit that Lady Gaga's repeat recycling of her act has started to bug her. "I do love her," Madge said of Gaga at a September concert in Atlantic City, but then snidely added, "Imitation is the highest form of flattery." The evidence against Gaga is pretty blatant: One in three of her outlandish red-carpet outfits and stage costumes appears to be straight out of the Big M's wardrobe. Of course, many of Lady Gaga's youngest fans may be wondering: Who's Madonna? Back in the day, Madonna was pretty much what Gaga is today: an overexposed, controversy-stirring, sex-tinged pop star with some mighty catchy tunes. She was certainly an original, though. Most modern pop divas can't say as much, at least not when they're in Madonna's company. Ø Twin Cities fans' 25-year wait to see the original Queen of Pop in concert again finally comes to an end with Saturday and Sunday's Xcel Energy Center concerts, but we've been seeing signs of her all along. Here are her biggest imitators.