Life's a Witch for Britney Spears at Barrymore Bash

The "Womanizer" singer gets down at a Halloween party

Britney Spears spent Halloween with Drew Barrymore.

Dressed as a witch (black dress, black hat and long black wig!), the comeback pop-star princess was one of an estimated 200 or so guests at a costume party at Barrymore's L.A.-area home on Friday night.

While Spears spent mucho time dancing at the bash, she got unexpectedly bashful and pulled her witch's hat down when the DJ played her hit "Toxic."

Also at the party, Drew's BFF Cameron Diaz...

I'm told Spears and Diaz both recognized one guy's costume right away—he was dressed as their ex Justin Timberlake's very tattooed character from the movie Alpha Dog.

As for Diaz, one partygoer reported, "I think she was a flight attendant. It was hard to tell."

Natalie Portman was Little Red Riding Hood. "T.R. Knight was a little devil thing," my source says. Amanda Bynes went as an ancient Egyptian, Liv Tyler as Charlie Chaplin, Ricki Lake also as a devil, Justine Bateman dressed as an Indian princess, and one of the Olsen twins was a geisha girl, while Chris Kattan was Luke Skywalker.

As for Barrymore, she was Melanie Daniels, Tippi Hedren's character from the Alfred Hitchcock horror classic, The Birds.

Anne Hathaway appeared to put the final nail in her relationship with jailbird ex-fiancé Raffaello Follieri by going to the party as a corpse bride.

—Additional reporting by Ken Baker