This game has hidden developer credits.
Monochrome-only Mac games were on the way out by 1991, but Creepy Castle had an excuse: this side-scrolling monster mash boasted a cast list out of a Universal Horror team-up. Dracula, the Wolf Man, Frankenstein's monster and his bride... they're all lining up for our wholesome hero to beat them down.
Each Mac OS Classic app used a four-character creator code to track its icons and documents, and Creepy Castle's was... COMB? What part of "retro horror beat-em-up" suggests choosing the word COMB?
The answer is found in this copyright string, left over from an early prototype, that contains the game's working title.
Combat, Version 0.1, Copyright 1989 by William C. Appleton