Continuity mistake: After the ball game, there is a cut over Miguel's eyebrow. Right after this scene, the cut has disappeared.
Continuity mistake: When Cortes comes to the El Dorado island, he sees that Miguel and Tulio's footprints lead directly from the boat to the jungle. But this is not what happened. Miguel and Tulio arrived to the island, bumped into two skeletons, ran back to the boat, walked around the beach for a while, and THEN went into the jungle. This is what the footprints should have shown.
Continuity mistake: When the two men are running away from the soldiers, they see two water barrels and there is no board underneath them. A second later, the men jump into them, and now there is a board underneath them.
Continuity mistake: When Miguel and Tulio first arrive to the island, they bump into a skeleton. When Cortes arrives at the island later in the film, there's only a skull. The bones that were there earlier have vanished. (00:14:50 - 00:39:50)
Continuity mistake: When Altivo the horse jumps out of the boat he has normal horseshoes, then after Cortes leaves he reveals his golden horseshoes, then when Chel stirrups him he is back in normal horseshoes.
Continuity mistake: The color of the weapon Tzekel-Kan uses to punch the victim into the whirlpool, changes from brown to white to brown again.
Continuity mistake: The armor of the soldier Tulio bumps into in the beginning goes from being shiny enough to see his reflection in it, to not shiny at all, to really shiny again.
Continuity mistake: The number of natives holding onto the ropes to prevent the giant statue from falling keeps changing in the final scene. There are usually several huge rows of them, but in some shots there are no more than 15 or so.
Continuity mistake: When the two men are climbing over the fence to get away from the bull, you can see that the the part of the fence they're climbing is made up of 15 planks, but in the very next shot it's made up of 9 planks.
Continuity mistake: During the sacrifice scene, Chel throws out petals from a bowl. You can tell the bowl is almost empty, but a second later the bowl is much fuller than it previously was.
Continuity mistake: While running away from the giant jaguar, Chel tells the men to get on the horse. In this shot, there is a throne standing in front of the staircase, but in the very next shot as the horse starts galloping away, the throne has disappeared.
Continuity mistake: When the men first arrive at the El Dorado island, their boat constantly changes position.
Continuity mistake: During the song "On the Trail We Blaze" Miguel and Tulio pass by a rock shaped as an animal with its mouth open and there are vines hanging over it. Later in the film, Tzekel-Kan leads Cortes and his men to this rock, and the vines hanging over it are different. (00:19:05 - 01:13:30)
Continuity mistake: When the two men arrive at El Dorado, someone runs off to tell the chief. This person has yellow clasps around his arms, but when he finally gets to the chief he is wearing red clasps.
Continuity mistake: When Miguel and Tulio first enter the city there are plenty of vines at the entrance. But when they sail out of it at the end, there are no vines.
Continuity mistake: As Miguel kisses the sand he bumps into a skeleton. The skull is the first part he sees. However when the camera rises over the skeletons, you can see the skeleton's arm is stretched out. It wasn't there earlier.
Continuity mistake: After Tulio and Miguel arrive in El Dorado, Miguel's earrings disappear and reappear between shots.
Continuity mistake: When the monster corners the two men at the edge of the cliff, there are no vines on the ground. Then after punching Tzekel-Kan, Tulio says "Tie him up" and vines have appeared.
Continuity mistake: At the start of the film, when Miguel wins the map, he rolls it up vertically. Later in the film, when they first arrive at the El Dorado island, he takes it out of his shirt and unfolds it horizontally.
Continuity mistake: When Tzekel-Kan introduces the ball-playing team, he states that there are 15 of them. In the next shot, as the team runs back to where they came from, there are suddenly only six of them. The number of players changes constantly throughout the entire ball game.
Answer: Miguel had just told Chief Tanni how loyal Tulio and he were to each other. Then he overheard Tulio saying to Chel that he wanted to go to Spain with her, ONLY with her "Forget Miguel." That's why Miguel was so upset, because Tulio excluded him from his plans and his life.