Why other artist are appering and Avril no?
well she's part of the song that's enough and gettin the main part...

Please. They could easily replace her one word part with Rihanna's fart and it'd still be the same.

Rihanna filmed the video for Cheers during the concert. No idea if it was filmed in its entirety there though. I do know for sure that Eminem was here though as I did see him at the after-party.

Jay-Z and Kanye have also been in and out of the island but they did not make an appearance at the show.