Protagonists of this podcast

So I'm creating a podcast about a guy, dubbed "the Shifter" by galactic law enforcement (the characters will call him by whatever name he happens to be using at the moment) who travels from planet to planet trying to thwart a secret society. Basically, the Shifter is an alien from a planet where a secret society formed a deep state. This guy worked for the government and discovered this secret society was developing a piece of technology that would allow them to infiltrate other planets' governments and take them over the way they had taken over their own. This tech can change the species of the user, allowing them to blend in perfectly with any given population. The Shifter knew he couldn't blow the whistle on this because of how deep it went, so he stole the tech along with the research containing the information necessary to operate it, and destroyed everything else, using the tech to protect himself. He travels the galaxy in a stolen cloaked starship, constantly changing his name and species to avoid being recognized, and collects anything he can that will help him bring the secret society to justice. The secret society wants the tech back, and they have framed him for terrible crimes so that he is wanted throughout the galaxy.

So I'm going to have this story be told from the perspective of two people who meet this guy and join up with him. (Eventually more people will join up and the starship will have a full crew.) I need to develop these characters. I'm thinking a brother and sister duo, although it could be boyfriend and girlfriend, two friends, strangers who meet just before they meet the Shifter— all I know is, I'm leaning towards a young male-female human duo. I need to develop their background, how they come across the Shifter, and why they join up with him. All the mysteries in the podcast will be unfolding through their eyes. When they meet the Shifter they'll know almost nothing about him except the name he gives them, which will probably change by the end of the episode, and that he's an alien (as far as they know. Since his true form is completely unknown to them, for all they know he could be a human after all. Sometimes they're not sure even he remembers what he was originally. Every time he uses the tech he'll turn into a crazy new type of alien, and the change is not temporary, it doesn't "wear off." If he ever wants to return to his original form— and I think there are a few reasons why he would consider never going back— he would have to use the tech to make that happen, because the tech actually restructures the user's physiology rather than merely disguising it. Remember that scene in Attack of the Clones where the bounty hunter reverts to her reptilian form after Jango Fett kills her? That wouldn't happen here.)

I think these two POV characters will come from a fairly diverse planet where aliens are common. I want to introduce the Shifter as an alien species, so it only makes sense for aliens of that species to be common in an area where he is trying to blend in. For example, say the planet's population consists of humans, blue three-eyed midgets, and green and purple-striped giraffe people. When the shifter is first introduced, we would at first think he's a blue midget named Lenjamin, and then at the end of the episode he uses the tech to turn into an infrared gelatinous dodecahedron and tells the POV characters to call him Craigory from now on. (He wouldn't change every episode, but I think having him change at the very end of the first episode would be a nice twist that sets an expectation going forward.)

 

And what is your question, exactly?

 

What kind of protagonists would be best to explore this story?

 

That would depend on your themes and the story arch.