A few weeks ago, I shared a post from my former blog about the Arrowverse and how it succeeded in building up its universe, whereas the DC Cinematic Universe didn’t, by way of how the Arrowverse creative team built its universe over time before rolling out various team-ups in crossover episodes.

The Arrowverse crossover I addressed in particular was Crisis on Earth-X, based on a storyline from the DC comics in which heroes of Earth-1 head to Earth-X, a parallel earth on which Nazi Germany won World War II and a group of heroes called the Freedom Fighters fought against the Nazis. Featured in that storyline was an Earth-X version of Superman called Overman.

The creative team adjusted the storyline so that two of the villains were Dark Arrow and Overgirl — the Earth-X versions of Oliver Queen and Supergirl — and the third was Eobard Thawne, taking up the guise of Earth-1 Harrison Wells as he did in the first season of The Flash. Their aims were not just to conquer another earth, but to save Overgirl — who flew too close to the sun one time and absorbed too much solar radiation — by taking Supergirl’s heart.

I watched the crossover again to see how well it holds up. The major criticism I would have is that, while the villain certainly gives a good reason for the Arrowverse heroes to team up, it’s hard to make such a villain compelling, though, and that’s the biggest weaknes of the crossover.

The most compelling villains are those who have a valid motivation, but their methods are highly dubious. As an example, Malcolm Merlyn is one of the Arrowverse’s most compelling villains, because his motivation is that his wife was murdered. Who wouldn’t relate to the grief a person would feel over the loss of a loved one, especially under horrific circumstances?

But what makes Merlyn the villain is his chosen response, and that’s to destroy the section of the city in which his wife’s murder happened. His theory is that, because so much crime happens in that section of the city, nobody living there is redeemable. So you have a character who nobody would argue is wrong to be upset about the loss of his wife — but is destroying an entire section of a city the right response?

That’s not to say the writers don’t try to give Earth-X Arrow and Overgirl a valid motivation — Overgirl is dying and Earth-X Arrow wants to save her. But it’s hard to get anybody to empathize with the movement they represent. After all, we know about the atrocities the Nazis committed in Germany.

Where the crossover really works is in the journeys the various heroes take. The writers explore themes of love, family and sacrifice, all which go back to the relationships the heroes have with one another and what we have learned about them over time.

It starts with the reason the heroes come together in the first place — to celebrate the marriage of Barry Allen and Iris West. It’s the love the two have for one another that Iris’ father, Joe West, says inspired him to have a loving relationship again — and, in turn, inspires Oliver Queen to ask Felicity Smoak to marry him.

I know there are people out there who aren’t fans of what’s been dubbed “Olicity,” but I actually liked how the writers handled the relationship in the crossover. The fourth season of Arrow saw the writers struggle with how to handle their relationship, but they do a better job of explaining Felicity’s reluctance to agree to marry Oliver: The last time they got engaged, everything went wrong.

This allows Iris West to step in and reassure Felicity, because so many things went wrong after she and Barry got engaged — all the way to the point that their wedding got interrupted by Nazis. Iris’ point is that all the obstacles she and Barry dealt with didn’t stop them from committing to one another and Felicity shouldn’t let the same thing happen to committing to Oliver.

Love ties into family when we explore two more storylines: the relationship between Alex Danvers and Sara Lance and the relationship between Jefferson “Jax” Jackson and Martin Stein.

Alex and Sara have a one-night stand, which makes Alex awkward because she’s not over her engagement that got called off. But as the two get to know each other better, and Alex becomes more determined to save her adopted sister (Supergirl), Sara is there to reassure Alex. Sara stresses how her own sister died and she won’t let that happen to Alex’s sister — not just because Alex and Supergirl are family, but because Sara considers them part of her team.

Sara considers the Legends of Tomorrow team to be her family and Sara sees Alex and Supergirl as no different. Thus, Sara convinces Alex that she can’t go off by herself to save her sister and that she will stand by Alex.

The relationship between Jax and Martin may be more compelling because the two have spent so much time as the superhero Firestorm. Jax, who never knew his real father because he was killed while serving in the military, looks to Martin as a father, which causes Martin to realize that he does see Jax as a son.

So when the two have the chance to take a serum that will remove the Firestrom matrix, Jax is hesitant to take it because he will lose his father. And when Martin is critically wounded while some of the heroes escape Earth-X, Jax effectively becomes “life support” for Martin because of the bond they share through the Firestrom matrix.

We then get the third theme — sacrifice — tied into the Jax-Martin relationship. Martin convinces Jax to give him the serum so he can take it, saving Jax’s life as the expense of Martin’s. The scene in which Martin sacrifices his life is one that still gets me choked up, knowing that Martin did it out of love for the man he considers his son.

The sacrifice theme continues with Supergirl, who Iris and Felicity attempt to save, but when they are unable to do so, Supergirl gives herself up rather than let Felicity be killed. And that same sacrifice theme comes right back around, when another attempted escape sees Earth-X Arrow confront them, only for Felicity to stand before Supergirl and refuse to let her be taken.

It’s those three themes that really make the Crisis on Earth-X crossover compelling and make it more engaging than it would have been otherwise. And that viewers have gotten to know so many of the heroes and what makes them relatable as people adds to the storylines explored.

None of it would have been possible, though, if the writers hadn’t taken their time to build the worlds they created and the characters they have introduced. Even if the execution in different episodes or seasons was flawed, the patience shown in building to these crossovers is what allows the themes explored to truly work.

The DC crossovers, along with my general fandom, is what inspired me to create my Arrowverse Elseworld. You can learn more by clicking here.