In the performance episode, the Top 2 contestants performed 3 songs. The fans have voted for their favourite contestants. Performances in this 2 hour special will include: The Top 10; This year's winner; Last year's winner; and more. Performances announced August 22, 2008: John Legend, Hedley, reigning Idol champ Brian Melo and Jully Black. Headliner will be Mariah Carey!
| Name | Type | Role | |
|---|---|---|---|
| Brian Melo | Guest Star | ||
| Jully Black | Guest Star | ||
| Mariah Carey | Guest Star | ||
| John Legend | Guest Star |