We're so happy for ya, girl! Happy 26th! It sure does seem like Brit Brit had a fantastical birthday celebration last night, and we're inviting you all to see some of it! Part one begins at the Four Seasons, where Britney and her entourage (including Sam and Alli) partied on the penthouse balcony... and there was a very big special guest. Can you guess who?

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Paris Hilton and Britney! Reunited, y'all!

More pix inside...