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)
Continuity mistake: When Ghashiun orders the sandbenders to ransack Appa's saddle, Appa's eyes are closed. In the next shot, they are open, then go back to closed in the following shot. (00:02:23)
Continuity mistake: After Meng gives Aang the tray of food and Sokka takes it from him, Aunt Wu shows up, and it shows a shot facing her front. In this shot, Katara's back braid is missing; then it reappears a moment later. (00:07:05)
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.