Vigo, the ghostly, painting-bound tyrant of Ghostbusters II was played on screen by boxer Wilhelm von Homburg, but, discontent with Homburg's voice work, the filmmakers brought in Max Von Sydow to perform Vigo's lines in an uncredited role. Just how did Homburg's voice acting stack up against the Exorcist star's? This video, posted by makeup artist William Forsche, goes behind the scenes of the movie and reveals the original, undubbed voice of Vigo.
For comparison, here is the final, dubbed version:
There are more details about the story of the dubbing at Spook Central. It seems that Homburg was not aware of the change until he attended a screening of the film.