"Which song are you the most excited for?" tweeted Glee's next guest star Britney Spears to her legions of followers (almost 6 million and counting), among whom must be a few million Gleeks. And while we can't wait for the montage of her greatest hits on tomorrow night's episode, it's the costumes that have us most excited! In honor her highly anticipated cameo, we've rounded up the most memorable of Britney Spears's style moments, both onstage and off. Sure we included the sexy schoolgirl look that Rachel Berry (Lea Michele) will wear and the VMA snake charmer ensemble that Brittany (Heather Morris, above) will don, but with so many looks to choose from, how ever did the writers decide? Click through our gallery below to relive the extraordinary style—both chic and shocking—of Ms. Britney Spears.