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)
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.