In terms of Avengers, he’s the team's Hawkeye. Even though he is smart, capable, and strong he still feels useless in his group basically because he is the comic relief sidekick and is the only nonbender of the group.

This episode is basically the culmination of his character arc dealing specifically with his internal conflict of insecurity. Insecurity fueled by abandonment and trauma, his constant skepticism and sarcasm being caused by the horrific war-torn world he grew up in and his joking demeanor being him struggling to hang on to any sense of childhood he lost.

It shows that the writers and animators weren’t interested in just comic relief, they relished in the nuance of how Sokka’s personality came to be. Sokka, the franchises comic relief character has a surprising amount of episodes dedicated to him. A lot of episodes in Book 3 are just one-offs that serve to finish character arcs. Much like “The Puppet Master”, this episode is another often overlooked episode in the franchise.

Watch avatar the last airbender book 3 chapter 7