If you want to make a big splash with your charity event, it helps to have friends in high places, and Sean Penn knows more than a few. Case in point: Penn's third-annual Help Haiti benefit, held in Beverly Hills on Jan. 11, lured none other than U2 to the stage for the first time in three years.

The band's surprise performance, which came during a busy weekend that also saw them picking up a Golden Globe, added an extra burst of superstar pizzazz to Penn's fundraising gala. Taking the stage at the Montage Hotel ballroom, they performed a set that included 'I Will Follow,' 'Vertigo' and 'Desire'; the evening also saw singer Bono and guitarist the Edge covering Leonard Cohen's classic 'Hallelujah' with Haitian vocalist Anaelle Jean-Pierre. (You can watch part of their performance above.)

The event reportedly raised $6 million in all, drawing a crowd of celebrities that included Emma Thompson, Charlize Theron and Anderson Cooper, who served as the event's MC as well as the winning bidder in an auction that left him with a sculpture made from Penn's decommissioned guns. Variety quoted Cooper as telling attendees, "I urge you to go to Haiti and see it for yourself. Haiti pulses with life. Tonight, we celebrate that life and that hope and that strength."

Aside from benefiting a worthy cause, U2's performance acted as a warm-up for what's sure to be a very busy 2014 for the band. While details are still sketchy at this point, the group is expected to announce an upcoming studio album -- its first since 2009's 'No Line on the Horizon' -- shortly, with a spring release reportedly on the table.