Professor Charles Xavier: Listen to me very carefully, my friend: Killing will not bring you peace.
Erik Lehnsherr: Peace was never an option.
In First Class, Professor X is made handicapped in 1962 at the end of the movie. In the previous X-men movie, he was walking when he visited the girl (Jean) in the mid 70s with Magneto.
In the bar, when Wolverine dismisses Xavier's offer to join him, Hugh Jackman ad-libbed the line "go f*** yourself". The line was originally written "F*** off".