When people tend to discuss the most difficult Sierra adventure games, there is one name that usually comes up more than any other: Codename: Iceman.
Released for DOS, Atari ST, and Amiga, the Sierra point-and-click adventure was designed by Jim Walls — a former police officer who had previously helped create the Police Quest series — and was notorious for its challenging mini-games, unwinnable situations, and its frustrating emphasis on military and medical procedures and protocols (listed in its manual).
As a result, it doesn't tend to command the same amount of fondness as Sierra's other famous series like King's Quest, Space Quest, and Gabriel Knight, instead often finding itself as the butt of various community in-jokes.
A good example of this is the recently released fanmade prequel Kidname: Iceboy from the developer Grayson, which had its world premiere yesterday, thanks to the Twitch streamer and adventure game podcaster Jess Morrissette.
Created in Adventure Game Studio, it serves as a hilarious parody of the 1989 original focusing on the early years of that game's hero, the Naval officer Johnny Westland, as he visits a submarine camp at the age of 10, in 1973.
There are a bunch of jokes that poke fun at JW's frequently naive and patriotic outlook on the world, as well as ridiculous cameos from American historical figures like the (then) US President Richard Nixon and Navy Admiral John S. McCain Jr.
You can grab the game for free from itch.io. Morrisette has also published a longplay of the game over on YouTube, which features a brief Q&A with its developer.