you can activate the cheat option and then shift-click the mailbox... there you can change your careers to all those in the game...
on top of my head there are:
Doctor
scientist
super agent
evil genius
master thief
astronaut
leader of the free world
cook
music (rock and classic)
sports star
there should be more but i cant remember them now
Hey thanks mate, in Sims 2 you would shift click on the newspaper, tried that didn't do mailbox though. Thanks.