Michael "Mike" Hanlon is a major protagonist of the Stephen King multiverse.
Serving as one of the main protagonists of the 1986 horror novel IT, a mentioned character in 11/22/63 (novel) and Dreamcatcher. He is also a minor character in Insomnia.
Vote which fictional character would naturally fit in-universe with a big-named franchise! No time-travel, no interdimensional crap, no "Pooh's Adventures", they would just exist in-universe.