''Michelle plays my enemy but we had kids the same age so they had play dates, and Mila was a real firecracker, entertaining all of us between takes,'' says Weisz, 42, who is married to 007 star Daniel Craig and has a six-year-old son, Henry, from her previous relationship with director Darren Aronofsky. ''It was funny because my character hates Michelle's character so much and I'd be torturing her and they'd yell, 'Cut!' and then we'd all be sitting together laughing!''

Inspired by L. Frank Baum's 1900 novel The Wonderful Wizard of Oz (and the classic 1939 movie starring Judy Garland), the prequel stars James Franco as Oscar ''Oz'' Diggs, a small-time circus magician with dubious ethics who is hurled away from Kansas in a hot air balloon and ends up in the Land of Oz. When smitten young witch Theodora (Kunis) finds him and brings him into Emerald City, he meets her menacing sister Evanora (Weisz) and is forced into a battle between good and evil when they turn against him and try to trick him into killing their sister, Glinda the Good Witch (Williams).

Director Sam Raimi - best known for The Evil Dead and the previous Spider-Man franchise - admits finding Glinda was his toughest casting challenge. ''We had to believe she truly was a good soul because the audience is so smart, you can't fake that,'' he says. ''But when you meet Michelle, you look right into her eyes and you can see she has a pure heart and soul.''

The books and the characters are in the public domain, prompting Disney's ambitious attempt to launch a new franchise if this investment, estimated at $US200 million, pays off.

The blockbuster was mostly shot on soundstages in Detroit, Michigan, where elaborate sets were built to create the magical worlds of Emerald City and the Land of Oz, and the women were all strapped into harnesses at various points to fly on zip-lines. Weisz can't help smiling as she talks about playing such an over-the-top role. ''[I] thought it would be fun to be a bit more flamboyant,'' says Weisz, who won a best supporting actress Oscar in 2006 for her role in the drama The Constant Gardener. ''My mum was a really big Joan Crawford, Bette Davis and Barbara Stanwyck fan, so as a kid I saw a lot of those movies and love watching women being really fabulous villainesses.''

Williams, 32, says she wanted to find a more three-dimensional take on Glinda. ''I did a lot of geeky research,'' explains the actor nominated for three Oscars (for Brokeback Mountain, Blue Valentine and My Week with Marilyn). ''I read what Frank Baum was reading when he wrote The Wizard of Oz series and sometimes these things give you really useful information about who he was basing characters on - like his mother-in-law was one of the early suffragettes fighting for the right for women to vote. So I don't have to think Glinda is fighting to liberate Munchkins and Quadlings when I'm playing her, but when I think about trying to liberate a group of people who have a personal connection to the author, then it comes alive.''

Kunis, 29, is a little less enthusiastic talking about her inspiration for playing arguably the flashiest witch in the story, transforming midway in the film into the green Wicked Witch of the West. ''You've got to … remember you are doing an over-the-top movie and it's not like we're making Schindler's List here,'' shrugs the actor, who was nominated for a 2010 Golden Globe for her chilling supporting role in Black Swan.

''You ask me how I acted her good and bad, but it's the same person. Take the green away and she's just a woman scorned.''

In the primate of his career

Zach Braff is exactly the explosively enthusiastic and highly amusing big kid that you expect. It is a reputation that landed him his role in Oz the Great and Powerful as Finley the flying monkey sidekick to James Franco's Oz.

"Some days the phone rings and it says, 'Sam Raimi wants to speak to you in his office,''' Braff says. "That's what happened to me. I didn't even know this movie was happening. I went to his office and he said, 'I think you're funny. I need someone who can improvise.' He put on the screen a rudimentary animatic and I started riffing as the monkey. Making him a little wise-ass, making him a little funny.

''Sam started cracking up and I was like, 'This is good, keep going,' and I started improvising little quips and he hired me. Then I got to go to Oz for six months, which is really Detroit."

The comedic actor, best known for his work on hospital comedy-drama Scrubs, is more than just a joker. He directed the acclaimed indie film Garden State, and won a Grammy Award for its soundtrack. He is rather professional about being funny.

"Those people who are 'on' all the time drive me nuts," he says. "But when its time to, on set, I love to. I'd say to Sam, 'I'm going to tell you every funny thing that comes into my brain. It'll probably some days annoy you, but take what you like.' Sometimes he'd laugh his ass off … sometimes he'd be like, 'Zach, the movie's not called Finley the Great and Powerful.'"

Braff is also a self-professed film geek. "Walking on the yellow brick road was pretty cool. There were so many of those moments, where you're kind of like, 'I can't believe I'm in a ''Wizard of Oz'' movie!' I would walk around the sets while the crew was still building them because I was in geek heaven."

And like all good geeks, Braff wanted a collector's item. "I wanted that monkey puppet so bad, but I'm not going to get that," he says. "I did get a yellow brick from the road, though. They had a truck load, as you can imagine." Giles Hardie

OZ THE GREAT AND POWERFUL 3D

GENRE Fantasy drama.

CRITICAL BUZZ Big stars, big budget and revamp of iconic story should attract a big crowd.

STARS James Franco, Mila Kunis, Rachel Weisz, Michelle Williams.

DIRECTOR Sam Raimi.

RATED PG.

RELEASE Thursday.