Hugh Jackman's Notable Cameo in X-Men: First Class

Hugh Jackman accepted the opportunity to cameo as Logan/Wolverine when he learned he would be the only character in the film to use the word 'fuck'. He improvised the line, "Go fuck yourself," after using 7 other takes to say, "Fuck off". The reaction from McAvoy and Fassbender to the different line was authentic.

http://www.imdb.com/title/tt1270798/trivia