The actress who turned down Julia Roberts' role in My Best Friend's Wedding

Julia Roberts starred in My Best Friend's Wedding. Photo / Getty

Julia Roberts was unforgettable playing the scheming, flawed, loveable Julianne Potter in My Best Friend's Wedding nearly 20 years ago.

Her character was the forceful, vibrant food critic who decides she's in love with her best friend Michael right as he announces his engagement to wide-eyed college student Kimmie.

The 1997 rom-com's smash-hit success was spearheaded by Roberts, but the role was originally given to someone else: Sarah Jessica Parker.

Sarah Jessica Parker starred in Sex and the City. Photo / Getty

Luckily for Roberts, SJP had already signed on to do Sex and the City (the series began airing in 1998) so had to turn it down.

That casting change ended up having a domino effect: Drew Barrymore was in line to play Kimmie, but once Roberts was installed as the lead, she pushed for Cameron Diaz instead.

Evidently she had a fair bit of clout, as the actress also managed to get her pick of Dermot Mulroney for the male lead.

A scene from My Best Friend's Wedding. Photo / Getty

Mulroney recently gushed about how much he appreciated being part of such a successful film.

"I have nothing but great memories of that movie," he told The Huffington Post late last year.

"There was a period shortly after it was out that was like, 'Oh, please, go away, leave me alone.' And that passed, and I'm back to really just, I can't believe that I'm in a movie that has that kind of staying power."

He also explained why he thinks the movie has remained so beloved over decades.

"I guess we can't call it a classic yet [but] there's so few [rom-coms] since then that were as well made or that just had the same kind of legs that this has," he said.

"It took me this long to actually analyse why that movie stands out from the crowd of romantic comedies - it's, she's a sad clown. It's a melancholy movie. And that's what's funny about it. It's like somebody slipping on a banana peel. We love that."

"And all of the other romantic comedies, they're focused on the girl and the guy getting together. My Best Friend's Wedding is the exact opposite. So I've just given away a secret formula."