"What I Don't Know" is the theme song for the television series Deathbringers. Originally performed by Namona Wallabangher's voice actress Avril Lavigne, the song is known for using pop punk and power pop for the genre, contrasting from the teen pop music many Disney Channel shows had at that time. By 2014, it is still considered to be one of Lavigne's best songs and one of the best Disney Channel theme songs from the early 2000s .
As years passed, the song has been covered by many artists, still keeping the pop punk elements the song had, notably Magnapop and Superfamily in English, Jenifer in French, and Crystal Kay in Japanese.
In 2021, Lavigne returned to preform the song for the live-action film of the same name, albeit with a more contemporary style, with Scott and Lukasz returning to compose for the song. A music video featuring this version was posted on March 26, 2021. The music video shows Lavigne wearing an outfit similar to Namona's, while clips from the film are being shown.