The Tales of Ba Sing Se - S2-E15
Other mistake: The Tale of Sokka: When Sokka delivers his final haiku to the girls, he inadvertently adds an extra syllable to the final line. In the close-up of him counting his fingers, the iris of his left eye is rendered over his hand. (00:14:42)
The Desert - S2-E11
Other mistake: At the start, when Toph says, "I can hardly feel any vibrations out here," Aang moves his head, and it briefly duplicates. Right after that, Aang seems to shift into another position without any animation, most noticeable with his head and face. (00:01:56)
The Tales of Ba Sing Se - S2-E15
Other mistake: The Tale of Aang: After Aang lets all the animals out of the zoo, he takes out his bison whistle and blows on it. As he does so, the way he holds his staff makes it so that it's going right through his head. (00:10:28)
Other mistake: When Aang is reading the letter from The Guru, as Sokka says, "What's a guru? Some kind of poisonous blowfish?" his right eye loses its white colour three times during the shot. (00:18:19)
Other mistake: When the group goes to hug Sokka before he and Aang go to Chameleon Bay, you can briefly see that Toph is incorrectly drawn with arrow tattoos on her hands, like Aang has. This happens very fast, but you can still catch it when watching the episode normally without pausing or slowing it down. (00:20:35)
Answer: The pirates are from the episodes "The Waterbending Scroll" and "The Waterbending Master" (They're the ones Katara stole the scroll from). The traveling musicians are from "The Cave of Two Lovers. The prisoners of war likely refer to the Kyoshi Warriors, the men of the Southern Water Tribe, and possibly Bumi and the other citizens of Omashu.