The first couple of seasons of The CW's Arrow felt like every episode had to end with some massive cliff-hanger or plot twist, to the point that they became expected not just in Arrow, but in all of The CW's other series. Though it can sometimes feel contrived, the Arrowverse has built a large part of its fanbase off the twists they introduce and develop.
Most of the other series don't necessarily compare to the original in this aspect, as the series was far more grounded and thus leaned into it more than the pop science fiction of Legends of Tomorrow, but that doesn't mean they didn't have plenty of twists to go around.
10 Mon-El Being A Prince
The story of Mon-El came with tons of twists and turns that made the second season of Supergirl great. The story gave the opportunity to explain the difficult relationship Krypton had with its sister planet Daxam, revealing that neither planet was a truly perfect society.
Then it also gave everyone Mon-El, someone who had powers that didn’t exactly care to use them responsibly until Kara provided an example for him. The character pretended to be a member of the Daxam royal guard until Kara finally met his parents, who revealed he had been the missing prince of Daxam the entire time, something that angered Kara enough to end their relationship.
9 Jeremiah Danvers Being A Member Of Cadmus
When Kara and Alex’s dad disappeared when they were younger, it deeply affected them both for years and when they finally learned he was alive it was one of the biggest moments of their lives. The character made a sudden return claiming he had escaped from Cadmus, but in reality, he had been bent to Cadmus’ will through years of being captured by them and experimentation.
Though everyone wanted the Danvers family to be reunited again, it wasn’t to be—Jeremiah eventually revealed his allegiances and even stole information on aliens living on Earth peacefully from the DEO to give to Cadmus. Turning the character into an enemy of both the Danvers sisters and the DEO was a bold move, though they weren’t ever able to pay it off.
8 Cyborg Superman & Martian Manhunter
When Supergirl introduced DEO head, Hank Henshaw, everyone expected the character to essentially become Cyborg Superman eventually. That’s the character’s fate in the comics, after all. This made it all the more surprising when it was revealed that Hank was actually the Martian Manhunter, who took over the DEO years ago after his life was saved by Jeremiah Danvers, Alex and Kara’s dad.
This made it all the more surprising when Hank Henshaw turned back up and revealed himself to have survived his attempt at hunting down the Martian Manhunter and taking his place as Cyborg Superman. Project Cadmus transformed him into a force that could work for them, though unfortunately the character never quite got into his awesome Cyborg Superman costume.
7 Barry Allen Becomes Savitar
Not all twists are good ones, unfortunately. The identity of Savitar was a major part of Season 3, but the story didn’t provide any good possibilities on who the character could be. When they revealed it, the story itself barely made any sense: Savitar was actually a speed clone of Barry Allen who was created... to fight Savitar.
The character’s existence is paradoxical in nature, and his only goal is to ensure his own existence by breaking Barry enough to create the speed clones in the first place. The entire goal of the third season is figuring out a way to break this paradox.
6 Moira Queen With Malcolm Merlyn
Moira Queen was the troubled matriarch who did everything to keep her family together while she was alive. But when she was discovered as having a part in the Undertaking, she was about to go to jail... until Malcolm Merlyn pulled some strings behind the scenes.
Though she got free, the real surprise was learning that Malcolm hadn’t just freed her for old time's sake, but to prove that he was aware that their time together had resulted in more than just a partnership… but Thea “Queen” being born as well.
5 The Identity Of Zoom
When Flash introduced another speedster in Earth-2’s Jay Garrick, the question immediately became: why is Jay so young? In the comics, the character is usually an older character and serves as a sometimes-mentor for Barry Allen.
But all became revealed eventually when it was learned that the person playing Jay Garrick had been Hunter Zolomon all along, having captured the real Jay Garrick and hiding him so he could continue operating as Flash on Earth-2.
4 Oliver Queen Becomes Spectre
Oliver Queen’s death felt somewhat unceremonious given everything that had happened over the series’ existence. The character went down early in the Crisis, but was eventually revived thanks to the aid of the original Spectre, Jim Corrigan.
Much of the surprise to this twist came in that no one expected the Spectre to show up, to begin with, nevermind give his powers over to Oliver. With this incredible power, Oliver was able to defeat the Anti-Monitor and reset the entire multiverse, giving up his powers once again. This new multiverse came with more changes, as Oliver was able to set several things right that he hadn't during his time as a human.
3 Sara Lance Comes Back
The story of what happened to Oliver and his family and friends on the Queen’s Gambit wasn’t finished in a single season. The character’s backstory unfolded over several seasons, as they explained what happened to Oliver on the island. Eventually, fans learned that Oliver’s friend and love interest, Sara, survived just like he did, only she was trained by the League of Assassins.
In many ways, Sara was everything comic fans wanted Laurel to be; she had the superior training, and quickly took to being a hero who was every bit as capable as Oliver was. She was even liked enough to eventually become one of the main characters of Legends of Tomorrow, leading the Waverider on adventures to save time.
2 Malcolm Merlyn Being The Villain
In Season 1 of Arrow, it felt like Oliver Queen was an unstoppable being unleashed upon Starling City. His superior training allowed him to make anyone he fought look like a clown... until he met the Dark Archer. Despite Oliver’s training, he was one-sidedly destroyed in their contest and set up plenty of speculation on who was behind the mask.
Fans were quick to suspect Tommy Merlyn, since the name fit for one of Oliver’s most well-known villains and it would have created a perfect tension with his old friend being now his worst enemy. But Arrow zigged instead of zagging, and fans learned that it was actually Tommy’s father Malcolm who was the true threat to The Hood’s goals.
1 Harrison Wells Being Evil
There still hasn’t been a twist as big in Flash as finding out that his mentor was actually his greatest villain. The thing most fans forget about Flash is that the entire series takes place within a timeline that’s been drastically changed from the original timeline, which no viewer has ever seen.
Thawne traveled back in time and killed the original Harrison Wells, who created the particle accelerator and then proceeded to pretend to be Wells for years. His goal required Barry to become the Flash so he could eventually use Barry’s Speed Force connection to go back to his own time. This reveal and betrayal was one of the best, most shocking moments of Season 1.