It's nice to see all the love for Dwight Frye here, and it really does seem to be for the actor more than the Renfield character. What he brought to Renfield was remarkable, unsettling and brilliant. The only actor I can think of offhand who could play the kind of character that became (a blessing and, sadly, a curse) the norm for Mr. Frye is Peter Lorre. We'll never know if Frye had Lorre's amazing range, his subtly (when called for) since he never got the breaks, remained a specialty act to the end, at least on film.