One Hour Photo (2002)

Why So Serious? The first film to truly mine the underlying shuddersome creepiness that Robin Williams could tap into (well, maybe the second following Mrs Doubtfire).

Undergoing a convincing physical transformation (man-beast Williams apparently had to de-fuzz a lot of his notoriously hairy bod for the role), Williams is all dead-eyed stared, albino blond hair, and Generic-Mart garb.

His Sy Parrish becomes slowly obsessed with the Yorkin family, whose photographs he develops. He's tipped over the edge when he is sacked from his job (prohibiting the theft of any more family snaps) and he discovers that the idyllic family life he has been fantasising over could well be disrupted by the father's infidelity.

It was Williams' performance that gave this movie its unique selling point, and deservedly so.

If they played it for laughs... How could the Yorkins not fall for perennial family favourite Williams? After charming his photo customers with his repertoire of funny voices, he seals the deal by continually slipping in prints of himself in humorous poses into their albums until they relent and adopt him.

See also: Good Will Hunting, Insomnia