the last thing you remember was your kingdom getting attacked and your family getting killed, kidnapped or knocked out by the fire nation, you have escaped but you ended up on a island Aang, Zuko, Katara , Sokka and Toph found you unconscious on a island and decided to take a closer look

Zuko: who is this loser?

Toph: oh shut up Zuko

Sokka: no but really! Who is this person! Someone from the fire nation!?

Katara: oh it’s probably impossible! They have burn marks on them plus they don’t have any fire nation suit or anything!

Aang: Katara is right! They don’t have any fire nation signs on them..!