Anne Hathaway was flattered when Rihanna told her they had similar butts.

The 35-year-old actress - who has two-year-old son Jonathan with husband Adam Shulman - was nervous about returning to work for the first time after giving birth on 'Ocean's 8' as she'd found it difficult to shed her pregnancy pounds, but she was quickly put at ease by director Gary Ross and her co-stars.

She recalled: ''It was really significant for me because it was my first movie after having my son.

''One of the lucky things about being in this business for so long is that I've really kind of come to terms with the pressure that you get to look a certain way as an actress and I don't beat myself up about any of that stuff anymore. But after I had my son, the weight was really slow to come off and so I was a different size than I normally am.''

The Oscar-winning actress was first reassured by Gary.

She explained to talk show host Ellen Degeneres: ''The director told me, 'That's great, we have eight women in this movie. We need to have as many body types up there as we can,' which I was really relieved to hear.''

But she was still nervous about what her co-stars, including Rihanna, Cate Blanchett and Sandra Bullock, would think of her.

She added: ''I walked on the set, and, you know, my weight's a little up and I'm just aware of it. And I walk on the set and I'm my jeans, and I've done my best and I'm going to love myself no matter what.

''And Sandy Bullock looks up and goes, 'Looking good, mama!' And it made me feel amazing! Cate Blanchett's like, 'Nice jeans, Hathaway!'

''And then Rihanna looks up and goes, 'Damn girl, you got an ass!' And I of course freaked out and loved it so much. I was like, 'Really?!' And she goes, 'You got an ass like me!' ''

Anne had a ''beautiful'' experience working on the movie, which also stars Mindy Kaling, Sarah Paulson, Awkwafina and Helena Bonham Carter, because everyone got along so well.

She said: ''To be surrounded by so much love and understanding, it was just great.

''It was just this huge love fest, which was great because there's this terrible rumour out there that women can't get along and, man, did we just murder that rumour. We just loved each other so much. It was just so special.''