Robin Williams was filming in Wilmington, Del., the last nine weeks in a role that Dustin Hoffman was scheduled to play.

For a time in 1987, Hoffman was set to do "Dead Poets" - both as its star and director. But Hoffman, notorious for the number of projects he has been associated with that have never happened, opted to do "Rain Man."Williams plays an unorthodox English teacher at a boys boarding school. The movie is about his character's "essential credo about teaching - basically pushing the envelope, taking a chance, even though other people may disagree, to find that true voice of your own.

"Pretty much, that's my own bottom-line philosophy," Williams says. "But I also love all the characters - the characters of the boys themselves are great, individually. I went to a private boys school . . . rigid like this in many ways.

"Everyone has one teacher in their life that affected them. Some people, if they're lucky, have several. I can remember two or three . . . the ones that gave you something beyond what the subject was"