Gran Gran's summary of the war ("Long ago, the four nations lived together...") is taken almost word for word from the intro to the original series.
In the original series, Aang is not revealed as the Avatar--either to the Water Tribe village or to the audience--until Zuko's demand that they hand over the Avatar and Aang admits who he is and hands himself over.
In the original, Aang could not fly without his staff, which he called gliding. In this adaptation, he floats on air currents while still not being able to fly freely.
This episode combines elements from multiple episodes from the animated series: The Boy in the Iceberg (S1E1), The Avatar Returns (S1E2), The Southern Air Temple (S1E3), and The Southern Raiders (S3E16).
The firebender ability to burn a person from the inside through touch was never displayed in the original series.