In neighbourhood mode, bring up the cheat
box and type in
boolprop testingCheatsEnabled true
Then go into Create-A-Sim mode, and before you make a Sim, hit Ctrl, N. You should get a window appear stating that debug clothes are active. If not, try
Shift, N.
With this, you can create new Sims with the genuine alien skin tone, Maxis heads
that are normally hidden, Social Bunny clothes and head, or work clothes.
Be warned - the beautiful alien Sim I made with this cheat crashed the game every time she had babies; I have no idea why. Treat the cheat as a beta, and save frequently.