Starring: Dee Bradley Baker, Mae Whitman, Jack De Sena, Zach Tyler
The Southern Air Temple - S1-E3
Other mistake: When the gang is in the Hall of Statues of Past Avatars, Katara points out the avatar cycle pattern of statues and Aang zeroes in on Roku's statue. The earthbender avatar statue next to Roku is of an unknown man with a sword, not Kiyoshi. (00:12:50 - 00:13:35)
The Library - S2-E10
Trivia: Wan Shi Tong is of one the few things in this show that is not a reference to Asian cultures, but to Ancient Greece instead. In their mythology owls were the symbol of wisdom and their goddess of wisdom, Athena, was often depicted with an owl.
Chosen answer: Toph had Katara use it to send a letter to her parents. It never returned.