Character mistake: During the debrief meeting with the generals, Roy states the Lima Project was "some 29 years ago" and "the ship disappeared approximately 16 years into the mission." A few minutes later, Roy narrates "I was 16 when he left, 29 when he disappeared." This of course is only 13 years into the mission. (00:11:27 - 00:15:03)
Character mistake: Some characters use the letter "s" at the end of a Pokémon's name when the plural of a Pokémon is just its name. The best example is when Pikachu says, "Roger must've sent the Greninjas to cause the car crash." Being a Pokémon himself, there's no way Pikachu, out of all characters, would say that.
Character mistake: In her first walk through the city with Dr. Ido, after feeding the dog her sandwich, Alita takes a flyer and reads it. Between the lines that read "Wanted" and "Murder" there is a line in Spanish that says "Querido para el asesinato." It should say "Querido por el asesinato".
Character mistake: Hellboy's stone hand is on the wrong side when he's fighting the first giant. (00:32:50)
Character mistake: When they infiltrate the military facility, Steve and Tony are trying to blend in. Steve wears his hat the entire time he's indoors. He's a soldier, taking his hat off when he comes through the door would be second nature to him. Not removing it would make him stand out as someone who doesn't belong - Steve knows better than that.
Character mistake: Right at the beginning of the movie, introductory technobabble. "In this canister, there's a solution of protons. The canister is attached to a rotor circuit that generates the protons to the speed of light." I believe the science genius and creator of time travel mixed up the words "generate" and "accelerate" here. (00:00:50)
Character mistake: At the start Smith takes a Krestal ballistic computer and barely holds it out to get wind speed. The proper technique is to hold it at arm's length into the wind.