Monk has seen many celebrity guest stars over the years, not the least of which being Tim Curry in the role of Dale J. “the Whale” Biederbeck III, an 800-lb. corrupt businessman and longtime mortal enemy of Adrian Monk (Tony Shalhoub). The Monk guest star was one of three actors to take on this distinctive role. Although the character only appears three times, Dale the Whale was noticeably recast for each appearance, a choice which may ultimately have harmed the Monk series’ handling of Trudy’s death.

https://screenrant.com/monk-dale-whale-recast-twice-reason-explainer/