Stephanie Pratt is taking it all off for a good cause.

Bunnies. The Hills star and sister of Spencer Pratt is posing nude for a new PETA iPhone app called "Be Nice to Bunnies." The point of the naked advertisement?

Drawing attention to PETA product testing on animals.

Apple deemed the app cover too risque, so she'll appear fully clothed on iPhones. But fear not, you will get to see Stephanie Pratt nude in the print campaign ...

We are all for banning animal testing on bunnies, but Stephanie Pratt might try eating one or two ... or at least some kind of protein. Girl's looking a little thin.

"I want to help consumers be informed and keep them compassionate," says Stephanie Pratt, even if all people will be doing is ogling her naked ... side.

The likes of Khloe Kardashian, Eva Mendes, Alicia Silverstone and Pamela Anderson have also shed all clothing for the fame-seeking animal-rights group.

PETA was pissed at Kim Kardashian for karelessly klutching a kitty, though, so being eager to remove all clothes doesn't necessarily endear them to you.

Stephanie Pratt: Would you hit it?