Credit: Jon Kopaloff/Film Magic; Donato Sardella/

AnnaLynne McCord says Kim Kardashian will be serving up plenty of attitude in 90210's third season premiere -- even if she isn't a mean girl by nature.

"The director kept saying, 'Say that really mean, Kim!' and she would be like, 'Um, okay...'" McCord, 23, told at the CW Summer TCA Party in Beverly Hills on Wednesday. "Kim is not mean -- she can't be mean! She was really sweet...she got some good moments in there."

Earlier in the week, Khloe blogged that she and Kim, 29, had a blast playing "exaggerated versions of ourselves," despite feeling a little nervous about filming their cameo.

"AnnaLynne McCord was  sooo sweet -- she really made it fun and easy for us," Khloe, 26, wrote. "How gorgeous is she?"

But the 90210 actress tells Us she wasn't sure what to expect when the famous siblings showed up on set.

"You never know when you have different personalities guest on the they want a certain kind of food that we don't offer, or do they want a certain thing done a certain way," McCord says. "But the Kardashians, they were so nice...I love that they do things as a family. Khloe was hysterical!"