Throughout the episode, Mai's nails change in color from natural to dark gray and back continuously
At the part when Aang, Katara, and Sokka go into the sewer passage, the order of them going in is: Aang, Sokka, Katara. When Sokka goes in, it changes the scene and it shows Katara going second instead of last. The new order is: Aang, Katara, Sokka.