William Hickey did the voice of Dr. Finkelstein. He is credited for the voice of the "Mad Scientist" in the movie's Credits. He is known for playing other older men in movies, like Finkelstein.
William Hickey was unable to continue his role as Dr. Finkelstein due to his passing on June 29th, 1997, only 4 years after the release of The Nightmare Before Christmas. The replacement for Finkelstein in the video game Oogie's Revenge was Jess Harnell.