The main character of the titular story of this collection. When Dinky says "eventual" it probably doesn't mean what you think it means.
If there was any doubt that the surname-less Dinky in The Dark Tower is our guy, he makes suspicious use of the word eventual.
The fellow with the white hair tried the door. It was locked. This seemed to please rather than upset him. “Dinky?” he said.
Dinky, it seemed, was the youngest of the three. He took hold of the knob and Susannah heard a snapping sound from somewhere inside. Dinky stepped back. This time when Ted tried the door, it opened easily.
- Part 2 / Chapter V / Section 3