In Raiders of the Lost Ark, Indiana Jones needs to cut a stick to the right length in order to create The Staff of Ra, a doodad that will tell him the secret location of the Ark of the Covenant. Those dastardly Nazis are building their own staff with the help of evil archaeologist Belloq, but when the heroes make their calculations using clues on the staff’s headpiece, Jones realises that the bad guys have got it wrong:
Omar: (Reading the headpiece.) This means six kaddam high.
Sallah: About 72 inches.
Omar: Wait! (Omar turns the headpiece over.) … and take back one kaddam to honour the Hebrew God whose Ark this is.
Indiana Jones: You said their headpiece only had markings on one side, are you absolutely sure? Belloq’s staff is too long. They’re digging in the wrong place!
So if six kaddams make about 72 inches, one kaddam must be 12 inches, or a foot. Therefore, the correct length for the staff is 60 inches, and this makes it only around five feet tall.
However, when we later see Jones carrying it (see the screenshot above), it’s a good foot taller than him, which means that either Indiana Jones is only four foot tall, or somebody in the props department wasn’t reading the script very closely…
(People have tried surprisingly hard to find justifications for the apparent discrepancy: see also the lengthy discussions of the problem on fansite Raider.net.)