John C. Reilly exudes noble pathos. He could make Frankenstein's Monster simultaneously sympathetic and frightening.
The untimely death of Caroline, Victor's beloved mother, is what inspires the scientist to begin investigating the possibility of reanimation. Rachel Weisz would make Mrs. Frankenstein more than just a martyr.
Dark, brooding, charismatic Michael Fassbender would be perfect as Victor Frankenstein, the brilliant, doomed, original mad scientist.
Hugh Dancy's amiability would make him a good foil for Fassbender's intensity, so we're casting him as Henry Clerval, Victor's nurturing childhood friend.
The only person who's kind to Frankenstein's monster is De Lacey, a blind man. Stately Ian McKellen—who, incidentally, played the older version of Fassbender's character in the X-Men movies—would give the part a special dignity.
Elizabeth Lavenza, the delicate object of Victor's affection, is a part tailor-made for Germanic beauty Diane Kruger.