J.M. Barrie was inspired to write the play after he developed a friendship with he Llewelyn-Davies family. Peter Lewelelyn-Davies referred to Peter Pan as "that terrible masterpiece." He later threw himself in front of a London Underground train at the age of 63.
Brian at The State I’m In, writes a nice review and history, including some interesting tidbits (as above), of the Peter Pan phenomenon, including the recent Finding Neverland movie with Johnny Depp.