AceShowbiz -

Ashton Kutcher surprised the people attending 2011 Teen Choice Awards when he broke into an impromptu karaoke of Katy Perry's song. The new lead actor of "Two and a Half Men" took stage to collect the prize for winning Choice Movie Actor: Romantic Comedy when he did the singing.

"I'd like to say thank you through the art of music," Kutcher said when accepting the TCAs surfboard. Wearing a casual beach attire; plaid shirt, dark-colored tee, aviator glasses and a straw hat, the "New Year's Eve" actor then covered Katy's 2010 summer song "Teenage Dream" and led the crowd to a sing-along.

Beside singing, Kutcher also gave fans a sort of financial advice at the Sunday night (August 7) awards show. "Here's the best piece of advice I got when I was a teenager," he told them. "Don't ever charge anything on a credit card if you don't already have the money in the bank to pay for it."

Ashton Kutcher took home Choice Movie Actor: Romantic Comedy for his role in "No Strings Attached". He beat Penn Badgley ("Easy A"), Josh Duhamel ("Life as We Know It"), John Krasinski ("Something Borrowed") and Adam Sandler ("Just Go with It"). He was presented the award by "The Vampire Diaries" cast Ian Somerhalder, Nina Dobrev and Paul Wesley.

Honoring young fans' favorites in music, TV, movie and non-traditional categories, Teen Choice Awards was opened by the Kardashian sisters and hosted by Kaley Cuoco this year. Jason Derulo, Selena Gomez and OneRepublic performed that night, and will.i.am served as a house DJ.