One aspect that makes a lot of films great is the music and Juno is no exception. Director Jason Reitman has stated that Ellen Page played a big role in selecting the types of songs Juno listened to:

At one point, I asked Ellen Page before we started shooting, ‘what do you think Juno listens to?’ And she said ‘The Moldy Peaches’. She went on my computer, played the songs, and I fell in love with it. Diablo and I discussed putting a Moldy Peaches song in it where the characters would sing to each other. I got in touch with Kimya Dawson of The Moldy Peaches and she started sending me her work, which was beautiful, and that became a lot of the soundtrack.

The song in the official trailer is Anyone Else But You performed by The Moldy Peaches but also by Ellen Page and Michael Cera.