When Indy elbows Marcus off of the tank, watch the centre of your screen.  A few shots later, you can see Marcus between Indy and Connery.  For about one second, it looks like Marcus is laying flat on his back and a second later, he raises his legs into the air.  It just doesn't look right but is extremely hilarious to watch.

The late River Phoenix, who plays the young Indy, played Harrison Ford's son in the 1986 movie "The Mosquito Coast."

The actress who plays the cameo role of Walter Donovan's wife is Isla Blair, who in real life is married to Julian Glover (who plays the part of Walter Donovan) but in the credits at the end of the film, her name is given as Mrs Glover and not Isla Blair.

When young Indy is in the lion's cart, he cracks a whip that cuts him on the top of his chin, hence Indiana's chin scar. But actually Harrison Ford got that scar when he crashed his car while trying to put his seatbelt on (ironically).

When Indy and Elsa go under the library looking for the knight's tomb, they encounter an ancient picture of the ark of the covenant. As Indy inspects it, a few bars of "The ark of the covenant" music from Raiders of the Lost Ark plays.

The beach scene where Indy's father frightens the seagulls into taking flight and bringing down the Messerschmitt was done with fake seagulls and real white doves. The beach was covered with fake seagulls for the wide shot, and the closeup shots were done with white doves and piles of loose feathers to further confuse things. The film crew had to use white doves because it turned out that they absolutely could not train live seagulls to do anything at all on cue.

Sean Connery was born in 1930 and Harrison Ford was born in 1942. Sean Connery obviously developed early...

In the scene in the zeppelin where Indy talks with his father, Harrison Ford and Sean Connery both elected to shoot the scene wearing no trousers because it was so hot and they didn't want to stop every ten seconds to wipe sweat away.

During the scene with Hitler in Berlin, there is one shot where some books to be burnt are shown. If you look closely, you can see that one is "Das Kapital" by Karl Marx.

While in the Zepplin Jones Sr. comments on not having his glasses on. If you look carefully the paper is upside down.

The plane Indy and his father boarded was actually a modified Stampe model. A similar modified Stampe (if not the same one) can be seen in the movie 'The Mummy.'

A German sentence which could be counted as a mistake: When Indy and company are taken by surprise and captured by the German troopers in the Grail temple, one of them shouts, 'Das ist ein Überfall' (it's the last sentence before the group is brought before Donovan and Elsa). This actually means, 'This is a robbery'. I can't tell, though, whether the script writers consulted the wrong material or if this is considered to be an inside joke for linguists.

Many shots of Connery & Ford are from the waist up, which is probably a good thing, as to cool themselves from the heat while on location in Spain, they shot the scenes wearing no pants.

Not a mistake, but a translation. During the fighting scene on the tank. Indy is punched and hits the periscope while the solders inside watch. One of the solders says to the other "The Americans - they fight like women" in German and then gets hit by the periscope. Funny scene as it is, but better if you understand German.

Indy's real name is Henry Walton Jones Jr., which is based on George Lucas' real name, George Walton Lucas Jr.

On the zeppelin, the Nazi shows around a flyer with Dr. Jones Sr.'s picture on it. At the second table, a woman shakes her head 'no' before even looking at the picture. Possibly just the character not bothering to pay attention, as could happen in reality, but worth looking out for.

Indiana Jones does not like being called Henry by his father (his proper name) and tells his father to call him Indiana. Prof. Jones replies with, "We called the dog Indiana". George Lucas created the character of Indiana Jones and he named the character after his pet Malamute dog, Indiana.

Michael Sheard makes an uncredited appearance as Adolf Hitler. Sheard played Admiral Ozzel in The Empire Strikes Back, which also featured Harrison Ford and Julian Glover. The film also features an uncredited appearance by Nick Gillard, who choreographed the lightsaber duels in the Star Wars prequels. All Lucasarts productions.

During the motorbike chase Harrison Ford's hair is longer and Sean Connery's beard is fuller. This is because this scene was filmed after principal photography had ended, but Spielberg felt a chase scene was needed to explain their escape from the castle. The shot of Connery against a blue sky when the tank goes over the cliff was also filmed later, which again is why his beard is fuller.