I've known about those for ages, at the moment everything points to them being disfigured Apex from failed gene therapy. Just a victim of the Miniknog. At the minute it's just a rare easter-egg sort of thing. There are a couple of those, one I can name that you can't access directly is the in progress Ocean Biome that with abit of coding can be accessed ingame. I guess technically you could play one but without any lore or such to base your character on, not even where your race came from or what it exactly is, I don't see that being fun at all, more a 'I'm being different to be different' kinda thing.
These things are known as Rainbow Villagers, or Rabbit Villagers, due to their rabbit-like appearance. They have the exact same dialouge as Apex NPCs, but they also have a couple of original lines that imply that they weren't always like this, and that they may or may not the result of Apex experimentation. They've been around since forever, but they're usually not spotted on planets unless you find a Rainbow Mini Biome, to which the likelihood of them being there is quite high. They're laughably incomplete and barely even implemented properly yet, if there are even plans to implement them fully at all. Don't get too attached to them.