Well, there may be another cheat here for this, but you need to live in a town with celebs
and "meet" them for this. This way, you just need to be able to be a celeb. Press [shift]-
[ctrl]-c at once to open the bar to enter cheats, and type "testingcheatsenabled true" in 
the bar. Then shift click on your sim, and there should be a button to choose celeb level.
You'll know it when you see it. Just follow the the buttons and be a celeb!