In South Park: The motto of the South Park planetarium, "Transmitte me sursum Caledoni" translates to "Beam me up, Scotty."
In Monty Python's Flying Circus: (the Science Fiction sketch) The first man to be transformed into a Scotsman is Harold Potter.
In Monster's Inc.: Boo has a Woody doll and a Nemo doll.
In Jurassic Park: The first dinosaur sighted - a brontosaurus - is eating gum leaves, which are actually mildly toxic to most herbivorous animals (except koalas!)
In Willow: The sorceress Finn Raziel first appears as a brush tailed possum (ie a native Australian marsupial.)
(Oh yeah. I never tire of this one -- The series M*A*S*H went for longer than the real Korean war.

)
-- anyone got more stuff like this because I wanna know --
The Borg was created by the producers to replace the Ferangi as their arch nemesis. The Ferangi were originally supposed to do it, but their characteristics didn't put them up for the job.
Here's an interesting fact: Trey Parker (one of the creators of South Park) usually names sexually promiscuous characters in his movies/shows after his ex-fiance Lianne, after he caught her cheating on him before their wedding. Notable examples are Lianne Cartman from South Park and Alferd Packer's horse in Cannibal! The Musical, and I think there might have been something in Orgazmo and/or Time Warped too. Also interesting is that Lianne Adamo frequently appeared in Trey's earlier works, as a dancer/choreographer in Cannibal! The Musical and she had a small acting part in Orgazmo as well.
In Harry Potter and the Chamber of Secrets: Guilderoy Lockhart (played by Kenneth Branagh) was based on JK Rowling's ex boyfriend.
(Sorry if I got the character name wrong -- I don't have my DVD copy with me to double check.)
In Chocolat: Pontouk the kangaroo, when he actually appears in the last scene, is not a kangaroo - but a wallaby.
In Fellowship of the Ring: During the filming of the party scene, Bilbo's cake (which actually had 111 candles) caught fire. If you look closely, you can see smoke on the left hand side of the screen as he makes his speech.

For more trivia, read my post entitled "Did you know?"
Tim
For more trivia, read my post entitled "Did you know?"
Tim
Can you give us a link?
Poltergeist, The protagonist died: Three films between 1982 and 1988 were rolled. The adolescent daughter of the first part was strangled by an ex- fiancč, and in 1988, Heather ÓRourke, the blond girl of 12 years who carried out the third part, she died suddenly of a rare disease.
Exorcist Two died during the running: The grandfathers of Pretty Blair and the brother of Max von Sydow died at the beginning of the running, in 1973. The room of the girl caught fire and stopped the running six weeks. The son of Jason Miller (Karras father, in the fiction) suffered an accident of moto. Several meters of the film disappeared. The figure of the Pazuzu demon lost way of Iraq (initial scene) and was found in Hong Kong. .
this is really obscure :s