Continuity mistake: When Rango was at the mayor's office, the mayor grabs out a jug of water, and he opens the lid. But in the next shot, the lid is sealed again.
Other mistake: When Rango is loading his revolver during the stand-off, he loads the bullets on the right of the revolver, however, the chamber is hanging from the left of the revolver.
Continuity mistake: Around the beginning of the movie, when Rango is called by the armadillo, he's shocked and drops the glass in his hand, followed by the breaking sound, but as the scene continues, the shattered glass is nowhere on the road.
Continuity mistake: The one arm on the doll is on the right side in the opening scene. After Rango falls out of the car, it has switched to the left. At the end of the movie, it is back on the right.
Continuity mistake: Near the beginning when Rango is being chased in the desert by the bird, while he is running there is no can in sight, a second later, Rango runs into one and the hawk gets its head caught in it.
Other mistake: When Rango and Rattlesnake begin walking toward each other and the clock strikes noon, there are only eleven chimes, not twelve.
Continuity mistake: In the scene where the passing truck blows Rango off the armadillo, he gets caught by a mud flap. (This is in the exact area where it was so hot, that the water from his glass dries up in seconds and his drink umbrella goes up in flames). But while he is stuck on the flap, he gets hit with a big juicy blast of watery mud off the road.
Factual error: The 'Mayor' says he's a Turtle, but he's actually a Tortoise. Turtles have paddle type limbs for swimming, not reptile like paws as depicted in the movie.
Continuity mistake: When Rango is stranded in the middle of the road, he is clutching a drinking glass in his left hand. For the rest of the scene (starting from when he molts), the glass switches to his right hand.
Continuity mistake: When Rango is given a gun and belt, the belt doesn't fit and falls to the ground. Given the thickness of the base of his tail, it would be difficult, if not impossible, for the belt to fall to the ground the way it does.
Continuity mistake: During the vending machine scene, besides the fact that he's hiding in slot D8, many of the slots are mislabeled. However, he is 2 positions in, so it would require $.50 to get him out, not $.25. And the slot on his right goes from having candy in the back, to having a different candy up front, then to being empty.
Continuity mistake: In the scene where the water tower falls on the hawk, the hawk is looking up at the water tower and it falls toward him, but in the next shot they show him buried by silt from the tower and the bird is facing the other way.
Answer: TV Tropes mentions that the big eye might be an enormous alligator, because alligators are known to live in sewers.
Alligator eyes are different from what was shown in the movie.