Sources claim the pregnant actress was reportedly shocked after seeing her Hollywood rival listed in fourth place on the poster - behind the film's leading men George Clooney, Brad Pitt and Matt Damon - while she was pushed down to last place behind minor stars Don Cheadle and Bernie Mac.
A movie insider is quoted by newspaper reports as saying: "Julia's not happy. She was in the original 'Ocean's' film - Catherine wasn't - and she assumed her name would be first."
Meanwhile, Julia has joked that expecting twins is "classic overachieving".
She told chat show host Oprah Winfrey: "I see some lovely woman walking down the street pregnant with one child and I think, 'What's the point? Go for two!'"
The actress, who is married to cameraman Danny Moder, also revealed her mother wasn't surprised when she told her she was having twins.
She said: "I told her, 'I'm going to have a baby. Well, actually two babies.' She said, 'Of course. We have twins in our family.' I'm 36! She tells me now?"