9. Gimli Was Played By The Tallest Member Of The Main Cast
One of the advantages of movie making is that, if you're clever like Peter Jackson, you can cast whoever you want in whatever role you want, and trick people into thinking the actors look WAY different than they really are.
When I was a kid watching Lord Of The Rings, if you had told me that John Rhys-Davies, who played the dwarf Gimli, was in reality one of the tallest members of the entire cast, it would have blown my damn mind.
John Rhys-Davies is over 6 feet tall, towering over Viggo Mortenson, which makes the fact that Gimli is like half his size in the movie hilarious. Peter Jackson felt constrained by his casting choices, and generally just wanted to cast whoever he wanted in whatever role he wanted. So to make it work, he used different scaled sets and scale double actors to create the illusion of radically different heights than the actors he cast actually were.
The fact that it's still impossible to see the cracks in this effect 20 years later is absolutely staggering.