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Which last minute replacements proved to be huge improvements?
Hugh Jackman - X-Men: It wasn't easy casting the role of Wolverine, first offered to Russell Crowe, who passed -- and Dougray Scott got the part. But scheduling conflicts with "Mission: Impossible 2" forced Scott to drop out, so Singer turned to Hugh Jackman, who joined three weeks into production. Six films later, Jackman's a superstar. Scott, meanwhile, is filming something called "The Vatican Tapes."MORE PHOTOS