Bill Watson is a character from The Shining. He is the ancestor of the man who built Overlook Hotel, and has been a member of the hotel since he was an infant. He is the on season caretaker on the hotel and mainly runs the boiler. He has a very strong hatred for Stuart Ullman, constantly denigrating the man whenever possible.
The Shining (book)
In the book, Bill Watson is a fat man, with fluffy hair and with a foul mouth, prone to swearing. He shows Jack around the boiler room and tells him how to maintain the boiler. He also tells Jack of how the incident in Room 217 happened and doesn't seem to show emotion or much sympathy for Lorraine Massey. After he leaves the hotel, he is never seen or heard from again, but he is mentioned and referenced a few times.
The Shining (movie)
Bill's character in the 1980 movie was completely altered and changed from his book counterpart. In the movie, he is tall, thin, has black hair and is rather quiet. He tells Jack that the job as a winter caretaker should be quite a change for him. He attends the tour with Stuart and the Torrances on Closing Day, not saying a word, but following behind at the very back. When Jack, Wendy, Stuart and him go down to the basement, he still doesn't say a word and after Stuart says that once everyone's gone, the Torrances will hardly know everyone was in the hotel, he is never seen or referenced again.
However, that doesn't mean his character is not without importance. The way director Stanley Kubrick cuts quickly to Bill's kind of "hang dog" expression right as Mr. Ullman begins telling Jack the story about Grady killing his family, Bill's entire purpose seems to be there to serve as witness while Jack hears this important detail, which of course becomes an important plotpoint later on. In his other films, Kubrick has used characters as mysterious onlookers before, and that's what Bill serves here. Basically, there would be little time, or purpose, to have Bill showing Jack the boiler room and talking badly about Mr. Ullman. While a novel can find space and time for these kind of details, a movie can only show and tell so much as the story is moving forward in a two-plus-hour timeframe. Bill, in the movie, while not important like the novel, does have importance albeit on the side of caution and mystery.
The Shining (miniseries)
Bill Watson is renamed Pete in the 1997 mini-series and plays a larger role than the book or movie, taking over most of Stuart Ullman's role from the book. His character is almost the same as his book counterpart. He gives Jack a tour of the boiler room on interview day, then on Closing Day, takes Jack and Wendy around the hotel a bit, mostly the kitchen and dining room area, joking and laughing and joking with them. Pete leaves the hotel eventually, cheerfully farewelling Jack, Wendy and Danny. He also farewells Dick Hallorann and then leaves the hotel. He is not seen again after this, but is referenced at times.
Bill Watson does not appear in Doctor Sleep at all but is referenced several times.