Meanwhile Pete Wentz splits his trousers!

Yeah Yeah Yeahs singer Karen O brought a smile to the face of the Carling Weekend: Leeds Festival this evening – and even she couldn’t stop herself descending into fits of giggles during her band’s Main Stage set.

Karen O, dressed in an amazing multi-coloured leotard, was in high spirits, constantly giggling and throwing herself around the stage.

It all got too much for her during ‘Phenomenon’, when she attempted to take off her hat. It got stuck and this triggered a fit of laughter, and she was unable to continue singing the song properly.

The band played a set which consisted mainly of songs from their second album, ‘Show Your Bones’, as well as older songs ‘Date With The Night’ and ‘Maps’.

Earlier in the afternoon, Fall Out Boy played an eventful set on the Main Stage.

At the start of their set, Pete Wentz’s trousers split. He told the audience he almost hadn’t worn underwear today and, with reference to the recent story on NME.COM concerning high demand for naked pictures of him, he said: “I don’t want any fucking naked pictures of me on the internet now, do I?”

Before playing hit single ‘Sugar We’re Goin’ Down’, Wentz divided the audience in two and told each half to throw rubbish at the other, after expressing sympathy for Panic! At The Disco frontman Brendon Urie, hit by a bottle in Reading yesterday.

Wentz said: “It’s like the Middle East. Let’s see how this fucking war plays out!”

However, following the crowd’s ‘war’, Wentz said: “We’re gonna declare a ceasefire.”

The band then played a very well-received ‘Dance Dance’, after which they told the front rows of the crowd to form a circle pit for the final songs of their set.

Speaking to NME.COM after the performance, Wentz said: “I feel, outside of Iron Maiden, we’re the best band to win a crowd over. Bottles are standard for Fall Out Boy, but it’s been really good at Reading and Leeds.”

Over on the Carling stage, Aussie rockers Howling Bells rounded off their 30 date tour with a downbeat set which was watched by Forward Russia[/a] guitarist Whiskers.

The band performed tracks from their self-titled debut including crowd favourite ‘Low Happening’, ‘Setting Sun’ and ‘Broken Bones’.

Stay tuned to NME.COM/festivals for full coverage from both sites of the Carling Weekend: Reading and Leeds Festivals including news, pictures and blogs, and check out next week’s issue of NME ‘ out August 30 ‘ for the ultimate festival review.