The Beastie Boys were originally slated to headline the Budweiser stage on Day Two of Lollapalooza, but when Beastie Adam Yauch announced he had cancer, art-rockers Yeah Yeah Yeahs immediately filled the slot. Mercurial frontwoman Karen O took the stage adorned in a peacock/Native American hybrid headdress with a feathered cape. Pretty typical, if you ask us.

But the Yeah Yeah Yeahs didn't lose sight of why they were there; at the end of 'Phenomenon,' the band went into an improved riff of the Beastie Boys' 'So Watchu Want,' sending the crowd into a frenzy. "This is a special event; you guys will never forget this night," she said between breaths to the audience. "We're not even supposed to be here. We'd never expected to fill the shoes of the f---ing Beastie Boys."

Throughout the hour-and-a-half set, Karen O removed her getup, messed up lyrics twice and tuckered herself out, all the while giving a marathon performance. Karen O was impressed with the crowd, yelling, "Best crowd ever!" She prefaced the next song as a summer love song and dedicated it to loved ones, TV on the Radio, Deerhunter and all the lovers at Lolla. YYY's burst into an acoustic and drumless version of their greatest hit 'Maps,' but when O forgot a lyric, she paused and asked the band to "rewind." Not letting the gaff deter her, she raged through their last song, 'Date with the Night.'