Debbie (Leslie Mann) is hitting a milestone birthday in the flick ‘This Is 40,’ and with the help of her husband, Pete (Paul Rudd), she does her best to pretend it’s not happening just yet. It’s hard to think of a song more tailor-made to soundtrack a coping-with-middle-age movie like ‘This Is 40’ than ‘We Are Young’ by fun., one of the year’s biggest hits. But we’re getting a little but ahead of ourselves here.

The ‘This Is 40’ trailer opens with another tune appropriate for the plot. “I’ve been working on my rewrite,” Paul Simon sings on ‘Rewrite,’ a song off the folk-rockers 2011 album, ‘So Beautiful or So What.’ Simon is singing about a veteran back from war, and Leslie is still in the thick of her battle against middle age, but both have combat experience and both are trying to change their lives. Will she succeed in this long-awaited semi-sequel to Judd Apatow‘s ‘Funny People'?

'We Are Young' certainly has changed the lives of the band fun. The song, which features singer Janelle Monáe, soared to the top of the Billboard Hot 100 charts, where it stayed for six weeks and helped sell nearly 300,000 copies of 'Some Nights' in the process.

Watch the 'This is 40' Trailer Featuring Fun.'s 'We Are Young'