"Little Miss Obsessive" is the first official single taken from third studio album, Bittersweet World, which is set to be released on April 22, 2008.

"Little Miss Obsessive" features the Plain White T's lead singer, Tom Higgenson, on vocals. The song is a mid-tempo track that goes back to Ashlee's musical style of the more pop/rock feel that she is mostly known for. It will be released on mainstream radio on March 18, 2008. "Little Miss Obsessive" was confirmed a single on a February 25 interview with Total Request Live and by her official website, which called it the album's "first official single".