Trivia: Just before the Gods Speaker finds the picture of the jaguar in the book, you see a picture of someone fishing off a crescent moon: the Dreamworks logo.
Trivia: Just after the two main characters stow away on the ship, the movie cuts to a nighttime shot that firstly shows the moon, then pans down to the barrels. The moon shown is the same moon that Dreamworks (the company backing the movie) uses for their logo.
Trivia: In the original script Miguel & Tulio were much more close, calling each other names like "darling", and becoming much more frustrated with each other when Chel came between them. The producers and other executives decided to remove these pet names and other references from the movie, but on some subtitles the pet names are still visible.
Trivia: The armadillo seen througout the film is named Bibo. Bibo is actually the french director Eric Bergeron's nickname.
Trivia: Chel's movements are based on Rosie Perez who voices her, who got her career break after being spotted dancing in clubs in LA.
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.