Trivia: When a Nazi falls from the back of the truck carrying the Ark, a "Wilhelm scream" can be heard.
Trivia: In the Well of Souls, you can see hieroglyphics of C3PO and R2D2 on the wall.
Trivia: On the plane to Nepal, the guy with the Life magazine is Visual Effects Supervisor Dennis Muren. (00:22:40)
Trivia: The filmmakers discovered to their chagrin that the snakes used for the Well of Souls sequence weren't afraid of fire at all - in fact, they would always try to get closer to the fire to warm themselves. At one point director Spielberg was caught on camera picking up a snake and telling it, face to face, "In the script, you're supposed to hate fire. Why do you like fire? You're ruining my movie."
Trivia: Pat Roach (the bald German mechanic in the fight at the plane) actually appears in all three films. He is a former wrestler, and is best known in the UK for playing "bomber" in "Auf Wiedersehen Pet".
Trivia: Another THX-1138 reference from George Lucas: When Indy gets off the Nazi Sub inside the hidden dock, you can hear over the loudspeaker, "ein, ein, drei, acht." (German for one-one-three-eight.)
Trivia: The film was originally given an "R" rating by the MPAA because of Belloq's death (his head explodes and showers everywhere). To overcome the ratings, Spielberg had flames superimposed over the image (although it thins slightly as the head detonates).
Trivia: The scene where Indy shoots the sword wielding bad guy wasn't in the original script. Three months' shooting had resulted in Harrison Ford having a nasty case of dysentery, and the choreographed fight would have taken three and a half days to shoot. Harrison Ford really didn't want to stay on set that long, so suggested that it would be a good alternative if he just shot him. Who actually suggested the change isn't certain, but it wasn't a spur of the moment decision, contrary to some thoughts - it was a planned alternative.
Trivia: The infamous sequence in which the three main antagonists are destroyed were achieved by: A) A hollow head model which got the air sucked out of it (Wolf) B) A head made of dental putty (which melts) under a heating lamp (Toht) C) A false head being blown off by a shotgun (Belloq).
Trivia: When Belloq is yelling at Indy on the island from down in the canyon, you can see a fly crawling about his face. He doesn't flinch, nor does he make any attempt to shoo it. It eventually ends up in his mouth, and he still doesn't react. In editing they removed the few frames where the fly flew off, in order to give the impression Belloq ate it (http://www.theindyexperience.com/interviews/paul_freeman_interview.php).
Trivia: When the Nazis have taken the ark from the Bantu Wind (Captain Katanga's ship) and no one can find Indy (until he climbs aboard the sub), Spielberg actually filmed Indy diving off the ship and swimming all the way to the sub. Harrison Ford did the stunt himself, though the footage was never used.
Trivia: The truck that Indy gets dragged under and the one that he blows up when he thinks he's killed Marion are actually the same truck. It was built specifically for the moving fight scene because they couldn't find a real truck that would work with all the stunts that were written for it. They used it again in the bazaar scene so that it would look like that type of truck was a common vehicle at the time.
Trivia: During filming of the fight scene around the German flying wing, Harrison Ford slipped and fell down and the plane's wheels rolled over his left knee, tearing his ACL. Rather than trust in the local medical care, they simply wrapped the knee up tightly, applied ice, and kept on going.
Trivia: For your entry concerning Indy's bazooka ambush and the fly on Belloq's face, there is an interesting additional item: not only does the actor not react to the insect, but the audio guy attempts to cover for him by adding two subtle buzzes - one on the right channel for its arrival, one on the left for its "departure". Best heard with headphones. (01:42:20)