Audrina Patridge and Lo Bosworth, The Hills

When Bosworth and bestie Lauren Conrad decide to throw Patridge a birthday party to smooth over tensions -- the three were roommates, but Patridge lived in the guest house -- Bosworth ended up leaving because she was uncomfortable with Patridge's friends. Later, Patridge told Bosworth, "We'll never be friends." Bosworth adds that Patridge also called her "super bitchy" on the premiere of the show's fourth season.