From Monkey Island wiki
Kevin Blackton is a voice and film actor whose voicework includes many video games. He provides the voice of LeChuck in his human form in the second, third and fourth episodes of Tales of Monkey Island, for which role he has been praised.
Blackton's role as the "human" LeChuck is unique; when the villain disguises himself as Charles L. Charles in Escape from Monkey Island or as Sheriff Fester Shinetop in The Secret of Monkey Island: Special Edition, the voice is still provided by LeChuck's usual voice actor, Earl Boen. Blackton is one of two new voice actors for LeChuck in Tales, the other being Adam Harrington, who filled in due to Boen's temporary unavailability.