I have plenty of bad memories of being stuck on the Vogon ship with no way that I could figure out to get the Babel Fish. I hadn't realized that I needed the junk mail from the second room in the game.
It gets worse -- there are a bunch of tools you go by throughout the game. If you fail to pick up any of them, that one will be the one you need to open one of the final doors.
It's a nasty little game, really.
I guess if I were doing it again nowadays I'd be going for a tool-assisted... umm... speedrun isn't really right here, so win-at-all-run.