Apparemment ya un sale bug dans le jeu xD
A couple of our readers are experience a game-freezing glitch in the PAL version of Super Paper Mario. The issue seems to pop up in Chapter 2-2. At a certain point, Mimi suggests that you investigate a number of rooms. Once you check all of these rooms and go back to talk to Mimi, the game freezes. Apparently a good amount of people are having this issue.
A solution that is working in some instances is setting the system language to German. This will allow you to progress past the glitchy point. You’ll be able to save after you get past the bug, and then you can power off and switch your language back. Huge thanks to Alexander and Superluigi for the heads up.
Au chapitre 2-2, lorsque Mimi vous dit d´aller voir dans toutes les chambres et que vous revenez la voir, apparemment le jeu freeze 
Si ça vous le fait, changer la langue du jeu en Allemand 