There's been some discussion and research going on in various Otherkin fora - especially given the vague and kinda unprofessional nature of the first contact. The offer appears aboveboard, in the sense that the channel in question has confirmed the existence and legitimacy of the casting call.
But that doesn't mean that participating is a good idea.
If you're considering taking part, please read the link above and make sure you know the way the Reality TV machine works. (tl;dr: "These people are normal!" does not sell commercials.)
And consider the long-term consequences. If you do this, you will spend a long time being defined not by who you are, but by who you presented yourself as to the TV. (Or, more accurately, who the TV makes you appear to be.)
You'll be recognized for years as "Oh, yeah, that guy who was in that otherkin TV show." It will be a lot like getting a tattoo.