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Julian Casablancas was temporarily a member of Arcade Fire this week. 

The Strokes frontman borrowed Win Butler's giant papier mache mask at the start of Arcade Fire's Lollapalooza Argentina gig on Tuesday.  But the group had barely started their first song before the real Win Butler ran out to unmask the impostor. Butler used some of his best acting skills to angrily kick Casablancas off the stage, saying this type of indie rock identity theft was "not cool." 

Casablancas was at Lollapalooza Argentina to play with his new band The Voidz.  They're set to release their first album sometime this year. 

Arcade Fire, meanwhile, are still supporting their hit album Reflektor, and are set to play Lollapalooza Brazil this weekend before heading back to the U.S. 

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