There's a hidden message in the graphics of the US release that reads "Ste & John were ere ok". This refers to Ste Pickford and John Pickford of Software Creations, the game's developer.

The US and JP versions were developed simultaneously, and since the JP version required much more space for the text graphics, there was a lot of blank space in the US tiles, so Ste wrote the hidden message there.

In the game's data are several unused sprites. Along with these unused files is an unused room, 07-02, in the ghost ship. The room has no doorways.

While Equinox is named Solstice 2 in The Japanese release of the game, the game's instruction manual does not state that the events of the game happen during a solstice or equinox; the instruction manual simply states that years have passed since the events of Solstice: The Quest for the Staff of Demnos.
The reason for the naming difference is unclear, although solstices and equinoxes refer to the distant between Earth and Sun, day and night, and the four seasons of each year.

Alan Smithee, a now-discontinued pseudonym used by the Screenwriter's Guild of America for film staff who want to disown a project, has seen use in the gaming industry - the earliest documented use of the name in a video game can be found for the director of Equinox for SNES. The game's real director, John Pickford, explained in 2023 that he went credited as Alan Smithee because he was "pissed" about the large volume of content removed from the final game.