The long-awaited crossover episode of Supergirl and The Flash has finally aired, and it was well worth the wait. Although he's from a different universe, Barry Allen fit right in with Kara and the gang, helping Supergirl out with Silver Banshee and Livewire, with just enough time for a quick race before he sped back to his Earth.
This was a fantastic episode, hitting all the right notes for a DC crossover —complete with tons of comic book Easter Eggs and hints about what Episode 18 could mean for the future of both shows.
Will We See Power Girl?
Ever since the crossover was announced, fans have been wondering whether the canon existence of "infinite Earths" in Supergirl's multiverse means that Power Girl could make an entrance to the DC TV Universe.
Power Girl is an alternate version of Kara Zor-El, trapped on Earth-1 after the 'Crisis On Infinite Earths' plot-line erased Earth-2 from existence. Currently, she lives as a refugee on Earth-1 and works with the Justice League alongside her counterpart Supergirl.
With the introduction of the multiverse to Supergirl, Power Girl could be revealed in later episodes. The title of Episode 18, "Worlds' Finest," is actually a reference to a comic starring Power Girl and Huntress: 'World's Finest' in the New 52.
Is this a subtle hint that Power Girl will appear in later episodes of Supergirl? It's definitely possible, although there does seem to be some crucial differences between Kara's universe and Barry's.
Barry pointed out that he hasn't encountered any aliens before, so we can assume Superman and Supergirl don't exist on Earth-1. Earth-2 is another matter; although Barry never encountered them in his trips there, the two heroes could exist in that reality. There's also the fact that S.T.A.R. Labs doesn't exist in Kara's universe, but has a huge role in The Flash and appeared briefly in Batman v Superman: Dawn Of Justice.
Is this just an easy way to explain the lack of The Flash in Supergirl's world and vice versa? Or is it a hint about future plots? This all remains to be seen before we consider future crossovers, and it could just be one of the many Easter Eggs and hints in S01E18.
DC Hints And Easter Eggs Galore!
If you include mentions of The Flash characters and allusions to episodes in that show, we counted more than 25 Easter Eggs in Episode 18. That's a lot. So here are the most interesting ones!
1. 'I Want The Blur'
Cat Grant is of course is the first to spot and name The Flash when he saves Kara from falling out of the CatCo building.
After considering a few titles, Cat settles on the Blur. This is a subtle nod to Smallville, as Clark Kent was dubbed the Red-Blue Blur, and eventually just the Blur, for years before assuming his role of Superman.
2. Silver Banshee Origins
We finally got an answer to how Siobhan Smythe is able to emit a sonic scream and it turns out that yes, this does line up with her magical DC Comics origins.
When visiting her aunt, Siobhan discovered that her powers originate from an age-old banshee curse. This is really exciting, as it introduces both magic and metahumans to the Supergirl world.
3. Livewire vs Blackout
In a tongue-in-cheek comment, Barry pointed out the similarity between Livewire and The Flash villain Blackout.
Appearing in Season 1, Blackout caused Flash to temporarily lose his powers, and generally wreaks a lot of havoc in Central City. He and Livewire can both control electricity.
4. 'Batman v Superman' Parallels
In an interesting twist, the day was saved not only by Supergirl and Flash, but ultimately by the people of National City, whose faith in Supergirl was restored by her heroic actions. In a neat inversion of Superman's heroic montage in Dawn Of Justice, a fireman reached out to Kara to help her up.
Although it felt a bit rushed, this was a nice resolution to the consequences of Seeing Red.
5. Infinite Earths
When Barry is explaining the multiverse, he mentions several Earths from DC Comics.
The world where the Nazis won World War II is Earth-X, the world where all our heroes are supervillains (and Lex Luthor is a hero) is Earth-3, and the world where John F. Kennedy wasn't assassinated is Earth-21. Basically, if you can think of a possible alternate Earth, it might exist in the multiverse theory. And it's even more likely that DC has already written a comic about it.
6. On Your Marks...
Finally, the race that Kara and Barry have at the end of the episode is a reference to Issue 199 of Superman, published in 1967.
In the comic, Superman and Flash have a race to discover who really is the fastest person alive. Previously on Supergirl, James told Kara she is actually faster than Superman himself. But is she faster than The Flash?
Episode 18 deftly avoided the question. Supergirl just about overtook The Flash when they first met, as she landed to ask him who he was. But later on, the race was actually Kara and Barry using their combined speed to project Barry back to his Earth. Until they meet again, we'll just have to wonder who really was faster!