I'm sure Alizée has burned her way into the hearts of many of the regular participants of Les Enfoires, including Patrick Fiori, Pascal Obispo, Christophe Willem, Jean Baptiste Maunier, Tina Arena, Nolwenn Leroy, and I'm sure there are more. All she has to do is mention to someone she is interested in being in the show and she and Gregoire will be in the show.
Edit:
During this show, Stars au Grand Aire, you can see how another artist is touched by the performer. She has touched many. If she wants to be there, she will be invited.
http://youtu.be/TzERQSwHszk?t=775