The Southern Air Temple - S1-E3
Corrected entry: When Aang goes into The Avatar State because he found Gyatso, statues and paintings of the previous avatars begin to glow all around the world, including the Fire Sage's temple. They act as is this was the first time, but Aang already went into The Avatar State before this point, when he thrown off Zuko's ship in the previous episode.
Correction: The Fire Sages are simply responding with astonishment to an event that is still relatively new to them, something that until very recently had not been happening for over 110 years. First time or tenth, it's still awe-inspiring to them.
Phixius ★