I think Infocom in general used the Grue in darkness. Seems like their game Starcross also had reference to the grue, until you were able to activate the emergency lighting in the yellow corridor. Also, there was a ruined cage in the zoo which had had a grue. Plus, if you asked the game "WHAT IS A GRUE," it would actually give you a description!In the game Deadline, if you ask "WHERE IS DUFFY," it would say "Like a lurking grue, Sergeant Duffy is always near the scene of a crime," and then continue with its description of him and how he can assist you.
They probably had other places, but I can't recall at this time.
I was an AVID Infocom gamer as a child. I credit those to helping improve my vocabulary (Literally needed a dictionary nearby at the start,) and also helping me learn how to type. One simple typo and you'd have to try typing the command again...or something adverse would happen!
