"It's a Britney/Brittany-off! Pop star Britney Spears posted the first shot of her guest spot on ""Glee"" Thursday, dropping a hint that she and Heather Morris (Brittany) were filming a scene inspired by her hit video, ""Me Against The Music,"" by tweeting ""All my GLEEKERS in the crowd, Grab a partner take it down."" ©FOX"
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