Aaaaaaaaaahhhhhh! Several scenarios are running through your head, and none of them are pleasant. Are ... are those aliens? They look a little more like lizard men. Wait, hold on. Maybe they used to be real astronauts, but encountered a space witch who turned them into whatever the hell those things are. Either way, you're here, and those creatures are here, which leaves you rightfully boned. Enjoy your last seconds on earth before you become the first victim in the cataclysmic event that's no doubt about to come down.
In reality, those creatures are nothing more than humble Iberian ribbed newts, who are very much from earth but just happen to look like the most alien-seeming bastards in existence. In their infinite wisdom and astounding lack of irony, several space agencies have hauled these critters to space in six separate missions, in order to study certain weird quirks of their fertility and regenerative abilities. Their fertility -- much like that of humans -- went a little haywire, and the space trip initially seemed to do little favor for their healing abilities. But once they returned on Earth, they actually appeared to heal faster. So, not only are we basically creating our own little green men, we're repeatedly exposing them to space to help them be more unstoppable.
Not that they need any particular aid on that front, because the ribbed newt's main method of defense is turning itself into a spiky murder machine by straight up poisoning its own ribs and SNIKT-ing them through its skin, Wolverine-style. Remember how I said you were "boned" earlier? Yeah, that wasn't a euphemism. You're about to be a shish kebab on the torso of a guerrilla salamander.