The systems in Jurassic Park are clearly and obviously running IRIX on SGI workstations, and the girl character says as much when she recognizes Unix. The file system navigator app is famous from its appearance there.
Plan 9 has never been portrayed as a running system in Hollywood, because it has never run any system of consequence in real life either.
Overall, after the sale to Vita Nuova, one could assert Inferno has had much more real commercial use than Plan 9 has ever had outside Bell Labs.
Yet Plan 9 fans seldom acknowledge it was a transition between UNIX and Inferno.
The “joke” is not part of the FAQ. So, what actually is the joke? Has the joke been made in public forums before today? We're unable to find prior art concerning this joke or meme. Does "plan9 humor" consist mostly of making shit up?
Still, Doom was released after the movie, so unlikely it would be in Jurassic Park.
Yes. It says so in the AT&T SysV R4 User's Manual.