Sean Penn sparks off Oscar buzz

american actor sean penn is already being tipped as a strong oscar candidate for his role as a retarded man fighting to keep custody of his child. in the forthcoming movie i am sam, the tough-guy star improvised throughout his performance, urged on by director jessie nelson — which left the cast and crew deeply touched. penn''s co-star loretta devine says, "oh my god, it''s just heart- wrenching.people would be crying on the set. sean is just amazing in it." i am sam also features michelle pfeiffer, who play''s penn''s attorney.