The list of Arrowverse shows that haven't done time travel is shorter--much shorter--than the list of shows that have. This week, it's Supergirl's turn. As our heroes try to track down Kara Zor-El, trapped as she is in the Phantom Zone, they realize that to get ahold of her Kryptonian DNA, they have to go back to a time when she was physically vulnerable--when she encountered Kryptonite in High School. Okay, sure. Spoilers follow for Supergirl Season 6, Episode 5, "Prom Night."

"Prom Night"

The premise for this episode is patently absurd. Even moreso than most Arrowverse shows, yes. The team needs to build a Kara Tracker, and for that they need some of her DNA. So do they go scan her apartment for loose hairs or discarded skin cells? No. They have to time travel. So do they go back to a time when Supergirl was Supergirl and would've been able to make sense of her friends needing her DNA? No, they go back to when the Danvers girls were in high school.

Between Flash going back to the 1990s and Supergirl to the early-mid 2000s, I'm starting to wonder if the writers were maybe working through something.

So while Alex, J'onn and Lena are staying in the present day/present time, Brainy and Nia make a daring attempt to get Kara's DNA from pre-Supergirl Kara Danvers. The former characters appear for a little bit at the beginning of the episode, but for all intents and purposes, this episode is all "A" story, no "B" story. We shift perspectives a little here and there, but it's just with Brainy and Nia in their time travel adventure.

Brainy and Nia's Excellent Adventure

This episode has two major strengths going for it. The first is the Brainy/Nia duo. For as much as the last season has been a struggle, the writers have done a good job of bringing both of these characters into the main cast. Brainy felt like a re-casting of Jeremy Jordan's Winn Schott, and casting Nicole Maines as Nia could've been simple stunt casting, but both the actors and characters they play are genuinely interesting.

For Brainy, the trouble is that he's used to being relatively disconnected from his emotions and is in the rather high-stress situation of trying to use his time-traveling ship to time travel again. The last time he did that, they ended up 12,000 years off-course. So he's still learning to cope with having feelings and having to do it in an especially difficult spot. Nia, meanwhile, is growing more and more powerful but still struggles with interpreting her abstract visions. Back in time, she knows she's in a place where her mother is alive, and gives into the temptation to call her. Nevermind the fact that she's trying to make a call from a 2021 mobile phone a full decade before the phone would exist.

SuperKids

The second strength is in the "youth" casting. This episode features three younger faces for main characters. Kara and Alex are once again portrayed by Izabela Vidovic and Olivia Nikkanen respectively, but a younger version of Cat Grant enters the fray as well, played by Eliza Helm.

All three look believably like younger versions of their adult counterparts. Vidovic and Helm especially do a good job of mimicking Melissa Benoist and Calista Flockhart. Either the actors are great studies, or they worked closely with their older equivalents, but there are all these little moments, ticks, and idiosyncrasies, that really drive home the feeling that these are the characters rather than just younger actors. It's genuinely impressive and almost enough on its own to carry the episode.

This is the first of a two-part episode that completes a couple weeks from now, so I'm reticent to judge it too harshly. The plot is pretty silly; the justification for going back in time is weak, and it once again feels--right now--like a distraction from the main plot. Filler in the final season.

Hijinks

There are some great moments throughout, though. At this point in her life, Kara was pretty sheltered; Alex was wholly focused on protecting Kara and, by extension, her family's privacy and safety. Young Kara meeting Brainy and Nia is fun and sweet--Nia ends up sleeping over at Kara's, and the two talk about having powers and coming from doomed planets, and it feels like Kara is for the first time talking to someone who fully understands her.

Similarly, Brainy ends up in some mostly off-screen hijinks when Kara's boyfriend, Kenny, takes him to the high school science lab so that he can build a 3D printer. While Kenny is in class, Brainy gets wrapped up in participating in glee club and baseball among other things, and is beginning to discover the ways teenagers cope with stress. This makes a lot of sense because while Brainy is clearly an adult, his experience with feeling things is quite fresh.

Old school

The big bad for the episode is a sort of classic golden/silver-age villain in terms of archetype: the zookeeper. It seems like every alien, mutant, or otherwise special superhero team encountered one of these at some point; an alien who wants to capture the hero and put them in a sort of galactic menagerie. The character looks like something out of an episode of the original Star Trek series with blue skin, flowing white hair, and an open vest.

The villain is silly, and the actors who play Naxim and his assistant Mitch (seriously, Mitch) both ham it up appropriately, equal parts menacing and ridiculous, and I'm hoping they're as much fun as they seem like when they inevitably encounter SuperKara.

Again, this is a weird episode--going for a two-parter centered around teenage versions of characters seems like a weird move. The strong cast makes it enjoyable to watch, though, even if it does feel a bit like filler.