Reviewed by Ben McClure.

Changing, the sixth episode of this season of Supergirl, debuts a classic Superman enemy to the program, the Parasite, showing up as a threat in series’ continuity for the first time. This is the sort of thing we should expect more and more as the series goes on: villains known in the comics for fighting Superman being introduced as appearing for the very first time, mainly in Supergirl’s life. The same thing already happened with Metallo, and the show also introduced Toyman as someone who hasn’t fought Superman. Who are all the villains that Superman has been fighting all these years? Just Reactron and Lex Luthor, so far.

But that’s ok, this is Supergirl’s show, and we like it when the program pulls out elements of classic super-mythology. It’s just that most of those moments are co-opted from Supergirl’s more famous cousin. But since the powers-that-be have decided that Superman is currently limited to guest appearances and disappointing movies, we’ll take what we can get.

The Parasite, for his part, has got a snazzy new alien-inclusive origin story, as Dr. Rudy Jones (played by William Mapother, who was creepy in Lost also) is infected by an actual parasite from space that turns him into a parasite. The story deliberately echoes The Thing with the creature being found in a dog (or was that a wolf?) in the tundra, in one of the series’ creepiest moment. The evolved Parasite itself is pretty convincingly realized by the production team, though he is perhaps a bit more disturbing than we’ve come to expect from this series. The Parasite’s actual murders are kept for the most part off-screen but the desiccated husks of people that he leaves behind are still pretty grisly.

One of the challenges with the Parasite in the comics is that there is often little to do with the character than to have him wander through the streets in a mindless rampage “to feed.” Changing does its best to give him actual character-based motivations, and thus a focus for his madness. The results are serviceable, but not inspired. It feels hastily written, with its surface-level talk about climate change and lack of explanation for things like how Kara and J’Onn are able to take the intended victim’s place in one situation without the guy ever seeming to realize that he’s in danger.

The action sequences are well done and it’s always exciting to see Supergirl and Martian Manhunter fight side by side. That said, it’s a little disappointing, though inevitable, that they were both get caught by the Parasite so easily. They both know what he’s capable of, and Kara especially should have been a bit smarter in the way she approached the thing. Still, the battle looks to have real consequences for the series as it continues, with M’Gann being forced to give J’Onn a blood transfusion. We don’t yet know the implications of this, but the twitching in J’Onn’s hands at the end is portentous.

Of course, the big subplot of the episode belongs to Alex, and her deciding to open up to Kara about what’s been going on in her life. Though the storyline feels like it is a bit to the side of the rest of the adventures of Supergirl, there’s nothing to fault in the performances in these sequences. Both Chyler Leigh and Melissa Benoist do a great job playing the love that is shared between sisters in the midst of an emotionally confusing situation.

Meanwhile, this week also sees the debut of James as the Guardian. The show is working hard to make sense of this, by inserting in the idea that brimming below the surface all along there has been this dream and desire to be a superhero. Like other things this year, it’s an obvious force, but as I’ve said before, James as the Guardian is way more interesting than James as the boss of a company that we’re not really paying attention to anymore. Eventually, we know that Kara will find out the truth and then the sparks will fly, but until then the Guardian costume does look cool and Mehcad Brooks seems more in his element than we’ve seen before. And the storyline gives us one of our episode highlights, which is Winn telling James off for treating him like a servant. It’s nice that the story is opening the door not just to develop James, but Winn as well.

Another great moment in the episode comes when Alex tells off Mon-El for stewing in a bar rather than helping anyone. It’s great to see him stepping up at the end without just automatically turning into a “superhero,” and the development comes just in time for Lillian Luthor to rear her evil head and kidnap him. Between that and whatever the mysterious aftereffects will be of J’Onn J’Onzz’s unexpected blood transfusion from a White Martian, the stage is set for some tense action and drama in upcoming episodes.

Score: 7/10