Filmed back in the day when Hollywood didn't care much about non-US audiences... The elevator killer, in 'The Man With Two Brains' is killing in Europe precisely BECAUSE nobody recognizes him. That's the gag.

There's also Steve Martins sadistic dentist from 'Little Shop of Horrors.'

And I'm quite certain that, great as he is in 'Buckaroo Banzai', John Lithgow isn't the only mad scientist in that film... If you ask me, they're all insane.

Others: for drama there's Gregory Peck in Hitchcocks 'Spellbound.' Russell Crowe as John Nash in 'A Beautiful Mind ,' David Morse in 'Twelve Monkeys' (and Brad Pitt is just plain mad, in that...)

On the lighter side, Lazlo Ollyfeld (sp?) from 'Real Genius,' Mike Myers as Dr Evil, and my favorite, of all time... Peter Lorre as Dr Einstein, in 'Arsenic and Old Lace.'