The Scot worked hard on his English accent before filming began - but Polanski was far from happy the first time McGregor spoke in character.
He tells WENN, "I spoke to Roman about playing the ghost with a Scottish accent and he said, no he had to be English. Also, he (character) went to Cambridge (University), so my first thought was that he would have a standard English accent; I find it difficult to do that accent without feeling kind of posh. I really wanted the ghost not to be posh.
"We were doing the wardrobe fittings and I hadn't read any of the scenes with Polanski and we had two days before we were ready to shoot. I'm trying on clothes and Roman appears every now and again and I said, 'Can we just talk, because if you don't like this accent I'm going to have to think of something else quick.'
"We finally sat down to read the scenes and he was much more picky about how I said the lines. Right from the get go he'd say, 'No, no, why would you read it like this?' And he'd take the whole script and read my lines for me until finally he said, 'Now you see!' I didn't know what I had done differently other than I was a little bit more frightened than I was a minute ago.
"The next morning I phoned up Roman from my car and literally read him some scenes using the London accent just to see if he thought it was OK and I wanted to double check. I actually double checked sneakily behind Roman's back with Robert Harris, the writer of the novel - and he said it was alright."
But McGregor only had to get his accent right; co-star James Belushi underwent a makeover.
The actor explains, "We shot Belushi for six hours with hair and, after six hours, Roman went, 'No, in the book he has no hair,' and they went away and shaved his head and we re-shot six hours worth of stuff with no hair!
"I didn't know how he (Polanski) worked, so I was slightly taken aback. He's a total perfectionist but I'm really fond of him. He was an extraordinary director to work with and a great collaborator and he keeps you on your toes. The first day we shot for 22 hours. I looked at him and thought, 'F**k, I've got four months of this!'"
Look in the sky. It’s a plane. It’s a bird. It’s a frog. No it’s just little old Underdog or as his young master so aptly calls him “Superman with a flea collar.” In Disney’s live-action version of the 1960s animated superhero parody the canine crimebuster (voiced by Jason Lee) returns to nip at the heels of arch nemesis Simon Barsinister (Peter Dinklage). Unlike the cartoon Underdog who took on human characteristics this pooch keeps all four paws on the ground Except of course when he’s zooming off to save the day. And it’s all thanks to the mad scientist Barsinister that Shoeshine—Underdog’s secret identity—runs as fast as a cheetah and flies like an eagle. Shoeshine turns into the Mutt of Steel after coming into contact with a serum created by Barsinister. His transformation from zero to superhero leaves Barsinister desperate to replicate the results of this lab accident for typically evil purposes. Assuming that is he can get his hands on Shoeshine who’s already found refuge in the Capitol City home of an ex-cop (Jim Belushi) and his son Jack (Alex Neuberger). With Jack’s help Shoeshine finds his true calling as man’s best super-powered friend. Oh and when he’s not thwarting jewelry heists he’s trying to win the heart of his very own Lois Lane “Sweet” Polly Purebred (voiced by Amy Adams). But Underdog must set aside his feelings for the King Charles spaniel when Barsinister and his dimwitted henchman Cad (Patrick Warburton) attempt to extort $1 billion from Capitol City. Let the dogfight begin! How wise of Disney not to unleash a computer-generated Underdog à la Garfield or Scooby-Doo. In or out of his formfitting superhero costume Leo the Lemon Beagle deserves a big juicy bone for his energy and resourcefulness. It certainly helps that director Frederik Du Chau knows how to work with animals having previously directed Racing Stripes. Beware though: Leo’s so darn cute that your kids will beg you for a Beagle for Christmas. Jason Lee who crosses over to the side of good after voicing The Incredibles’ malevolence Syndrome makes Underdog as humble and affable as his TV alter ego Earl Hickey from My Name is Earl. Still there are times that Lee’s so laidback with his narration you’ll swear you’re watching an episode of My Name is Underdog. Amy Adams delightfully kooky in Junebug makes for a surprisingly bland Polly. Brad Garrett though makes sure the bullying Rottweiler Riff Raff’s booming bark is worse than his bite. As for the humans K-9’s Jim Belushi is once again upstaged by a canine costar and Alex Neuberger does nothing to suggest he’s got what it takes to be the next tween heartthrob. Disheveled and disfigured Peter Dinklage is suitably hammy as the maniacal man of science. A bleach-blonde Patrick Warburton continues to exploit his Seinfeld fame by playing yet another Puddy-like himbo even though this act lost its novelty many dog years ago. Superheroed out? Then it’s certainly not enough for director Frederik Du Chau to make us believe a dog can fly. That said this Underdog is more for pups than parents. If your child’s never seen an episode of Underdog they’ll certainly get a kick out of the obvious efforts to spoof Superman from our hero’s phone-booth costume changes to his struggle to retain his secret identity. Du Chau doesn’t show much imagination when it comes to chronicling Underdog’s pursuit of truth justice and the American Kennel Club’s Way but at least he gives the predictable proceedings some oomph. He also keeps the poop jokes to a bare minimum and avoids making the kind of sexual innuendos that ruined The Cat in the Hat ensuring this four-legged superhero offers nothing but good clean fun for kids who have grown tired of Ratatouille. Parents though may find themselves wishing they were watching Spider-Man 3 again. Underdog makes no effort to appeal to anyone who isn’t suffering from a severe case of arrested development. Sure those weaned on the cartoon should come away mightily impressed with Underdog’s efforts to stay as true to its source material as possible. But there are only so many times you want to hear Underdog rhyme while he fights all who rob and plunder. Kids though will certainly walk out of the theater singing the beefed-up theme song and rooting for Underdog to save another day.