Look out for the claws on these resident mean girls of reality TV
Lauren Conrad and Heidi Montag, The Hills
The former friends became archenemies after Conrad accused Montag and her boyfriend Spencer Pratt of spreading a rumor that she had a sex tape with her ex, Jason Wahler. The two have rarely spoken since their famous confrontation -- when L.C. shouts, "You know what you did!" -- but seem to put the past behind them in the MTV show's upcoming fifth season.
Credit: MTV; Chris Weeks/WireImage.com