Penn (seasons 2 to 7)

I like that it shows us some characters who have been there since the beginning (even if in a small role). For example, Penn, we saw him in season 2, I think, when Indra goes with some Trikru to attack the Reapers and take hostages. And he has a bigger role in season 7 as a guard at Sanctum; moreover, he's very loyal to Indra.