Opening Remarks
Planning out the development of a multi-show shared TV universe months or years in advance is presumably rather hard. Ideally, clues to future storylines can be planted years in advance--creating gratifying and mind-bending "full circle" moments. Storylines sometimes go differently than planned, however, and inevitably some of these clues will never be returned to. That's what I'm interested in today: seeds of future storylines that have not been and almost certainly never will be followed up on.
I am excluding anything that could be explained as just an Easter Egg from this list. For example, movie posters showcasing Blue Devil have shown up in the Arrowverse more than once. Blue Devil could one day appear on one of the shows, but even if he does, those posters were surely just intended as a comics-reference Easter Egg for observant fans. This list is only for elements the writers put into the shows specifically in order to seed future storylines. In other words, most of these teasers have no particular comics relevance or entertainment value without a resolution.
Also, I am not including cases where plans had to be changed because of bureaucratic malarkey at Warner Brothers. For example, Ted Kord and Harley Quinn were both seeded on Arrow (rather overtly), never to actually appear. I am more interested in cases where the course of Arrowverse storylines simply strayed in a different direction than the writers may have at one time anticipated.
The list is ordered from most to least prominent teasers. In other words, the entries near the top were probably noticed by many viewers, whereas the ones near the bottom are really very obscure.
Where did Deathbolt get his powers?
Episode A3x19: Jake Simmons aka Deathbolt arrives in Starling City, robbing banks and earning the attention of brand-new superhero the Atom. Naturally, Team Arrow assumes that Simmons is just another particle accelerator-empowered criminal from Central City, like every other powered person they are aware of. Therefore, after defeating Deathbolt, Ray delivers him to STAR Labs for incarceration in the Pipeline. But before Ray departs for home, Cisco tells him that Simmons was actually in jail in Opal City the night of the particle accelerator explosion. So where and how did he get his powers?
This is definitely the most prominent unresolved teaser on this list. The writers were very explicitly seeding a future storyline with that scene between Ray and Cisco. My guess is that Deathbolt's origin would have tied into a solution to The Flash's annual "where are the new metas coming from this year?" problem. It was probably later that the writers decided to go the Multiverse route for season 2 and therefore scrapped whatever storyline would have explained Deathbolt. At this point, it seems that the story of Jake Simmons is destined to be an unsolved mystery of the Arrowverse...
Barry built Gideon?
Episode F1x20: It's a big moment. Barry, Caitlin, and Cisco locate and enter Evil Wells' "time vault" for the first time. Upon entering, they are greeted by Gideon, Eobard's future-tech AI assistant. Gideon reveals that Barry actually built her (in the future), and therefore she is compelled to obey his instructions. She proceeds to drop a few tidbits about the future (like that Barry is a founding member of the <REDACTED>). At that point, Evil Wells arrives back at STAR Labs and Team Flash is forced to quickly withdraw before being discovered.
Of course, starting the next year, Gideon was recast as a major character on Legends of Tomorrow as the Waverider's AI. The relationship between Eobard's and the Waverider's versions of Gideon has never been established. In fact, Team Flash has inexplicably never even spoken to Gideon since that scene in F1x20. Who is Zoom? Who is Savitar? Who is the Thinker? How can Barry defeat these foes? Gideon could trivially answer all of these questions. Apparently, the Flash writers' solution to this narrative flaw has been to just hope that the viewers forget she ever existed. That line about Barry having built Gideon, though, suggests that--at one point, at least--Gideon played into the writers' long-term plans for The Flash. At this point, I seriously doubt her existence will ever be acknowledged again.
UPDATE (8/7/2018):
Guess I was wrong. They did actually get up the nerve to acknowledge Gideon again in season 4, though her appearance was so menial it's hard to get too excited about it. They made no use of her history or knowledge of the future, instead just using her as someone for Harry to talk to. Certainly no reference to Gideon's origin or relation to the Waverider's Gideon.
Merlyn's got Vandal Savage in a bottle?
Episode A4x08: In the Year 4 crossover ("Legends of Today"/"Yesterday"), Teams Flash and Arrow deduce that only an artifact that had been exposed to an Nth metal meteor can harm Vandal Savage. The Staff of Horus is the most available such artifact, and Barry and Oliver use it to disintegrate Savage, apparently killing him. Cue Malcolm Merlyn, who sneaks in later and sweeps Savage's ashen remains into a little bottle for safe-keeping, dropping a line about how Savage will "owe him one." Legends of Tomorrow later revealed that only Chay-Ara can truly kill Savage--so he must somehow regenerate before the year 2147 (where he shows up next in L1x13). To make things worse, there's also the revelation that Savage had access to time-travel, which further confuses his whole history!
So what the hell really happens to Vandal Savage between 2015 and 2147? Does Malcolm somehow help Savage regenerate, or does he do it naturally on his own? Does future Savage travel back in time to un-ash-ify his past self? Is Savage really decent enough to reciprocate Malcolm's favor? Do Malcolm's acolytes (i.e. Athena?) still have his ashes in the present day, or are they stashed somewhere secret? Is Malcolm even really dead!?! Sadly, none of these questions will ever be answered (okay, maybe that last one will). After the response to Legends season 1, I think the general strategy has been to ignore Vandal Savage's existence, not draw attention to it (a little self-parody in L2x09 notwithstanding). Probably a good call.
Diggle the artist?
Episode A1x21: In the last episode, Oliver abandons Diggle to face Deadshot alone, leading to the deaths of several ARGUS agents and the escape of the World's Greatest Marksman himself. Understandably peeved, Diggle quits Team Arrow, leaving Oliver and Felicity to face the very imminent threat of the Undertaking alone. Though he regrets betraying John, Oliver is of course too proud to apologize to him, so Felicity takes it upon herself to mediate a reconciliation and goes to visit John at his apartment. When Felicity enters, the first thing she notices is a half-dozen distinctive paintings very prominently hung around the apartment with complimentary accent lights. She asks him if he painted them, but he mysteriously changes the subject immediately.
Since that one scene, the question of Diggle being an accomplished painter has never been readdressed. A couple of the paintings are reused in the set for Diggle's bedroom from episode A2x06, but the accent lights are omitted and they are not mentioned in dialogue. Diggle's bachelor pad is not shown on-screen again, since he and Lyla move into a new, larger apartment between seasons 2 and 3. In the new apartment, the mysterious paintings disappear completely. Apparently, the writers at one time envisioned John Diggle as some kind of closeted artist, but later ditched that angle. Or maybe John has just gotten better at keeping his secret hobby a secret...
UPDATE (3/9/2018):
Actually, I spied a couple of the paintings in the background of John and Lyla's apartment in A6x06 a couple months back. I guess some lovely person in the props department still hasn't forgotten Diggle's artistic bent. Keep the dream alive!
The mysterious stone carvings of Lian Yu
Episode A1x01: That's right, the very first episode of Arrow. More than that, just 30 seconds into the very first episode of Arrow! A bearded and barefoot Oliver runs through the forest of Lian Yu to light his bonfire and signal the passing fishing vessel. He arrives to this very ornately carved stone where he had previously stashed his hood, bow, and arrows. He strikes his flint arrowhead on the stone itself, then fires it to ignite the bonfire from afar. Starling City, here we come!
I love this one simply because it's literally the very first mystery seeded on the show (and by extension in the shared universe). Also, it's so quick and subtle that I totally didn't even notice it the first time I watched the episode. Of course, the first time I watched the episode I had no idea I was gonna end up loving Arrow so much and caring about all these tiny details!
As for what the significance of the carvings is, your guess is as good as mine. An arcane map? A mystical seal? A religious work of art? Lian Yu has quite a storied history as a primordial nexus of magical energy, Japanese WWII stronghold, Buddhist holy site, and Chinese super-prison, so there is certainly no shortage of possible explanations for the enigmatic carvings. Of course, with Lian Yu now rather irreversibly blown to hell, it seems that the mystery of the stone will have to remain just that: a mystery.
UPDATE (5/4/2018):
Genius idea! The Legends should visit Lian Yu (centuries in the past) to fight some sort of magic-y monster. It's already been established that Lian Yu is a "nexus" for magical ley lines (as are Star City and Hub City), so it's sound comic-book logic that Constantine's demon uprising would manifest there. Then they can establish that the stone runes were created by some ancient mystics as a way of containing the monster. Perfect!
An asteroid in Purgatory?
Episode 1x10: In the midst of an ambush, Oliver wrestles with one of Fyers' mercenaries and the two of them take a tumble down a steep hill; the merc lands hard on a rock and dies instantly. For those of you keeping track at home, this is Oliver's first (human) kill, though it is unintentional. After collecting himself, Oliver rather cleverly decides to steal the mercenary's clothes. He proceeds to inspect the map of the island he finds in the uniform's pocket and locates a prison camp where he expects Fyers may be holding Yao Fe.
In the corner of the map, a strange circular bay is visible. It is marked "asteroid bay" in printed Russian and "METEOR IMPACT -- HIGH MAGNETIC" in handwritten English (as far as I understand it, the difference between asteroids and meteors is simply one of size). The screencap above is actually from the beginning of A1x11 when the map is shown again a bit more clearly--in fact, the map continues to show up for the rest of season 1. Since then, the distinctive shape of the asteroid bay has continued to show up on maps of the island (which have remained remarkably consistent over the years), but never again with specific annotations.
This one is my absolute favorite entry on this list, simply because of how incredibly obscure it is. I honestly wonder how many people in the world are aware of this besides myself (and whoever made up the map). The map is full of other fun tidbits, too (that is, if you care as much about the geography of Lian Yu as I do). However, this is the only map detail that could have implied any storyline potential, in my opinion.
Out of all the "teasers" on this list, this is the only one that I really believe may never have been meant to seed future storylines. It is entirely possible that whoever was making up the map just wanted to include interesting things to make it more varied. However, I honestly do find it more likely that this "Asteroid Bay" was conceived as a potential plot device that could have been used to trigger the storyline for one year of the flashbacks.
The map mentions some kind of electromagnetic radiation. Of course, in real-life such a thing is rather unexciting, but in the world of comic books the words "asteroid" and "radiation" trip all kinds of red flags! Perhaps, if the decision to introduce the Flash had not been made, this meteorite would have been Arrow's gateway into the world of metahumans and superpowers. Maybe it could have been the meteorite that gave Vandal Savage his powers. Any number of very exciting things could have happened, but I think--in the end--no one's gonna complain about getting a dedicated Flash TV show, instead.
Closing Remarks
What a fun list! I wish I could think up more ideas for lists like this, because I really enjoy making them. There's something really quite satisfying about scraping the secret underside of the Arrowverse. What a totally ridiculous way of putting that... why did I write it like that? Well, it makes me laugh, so I'm not changing it now.
Anyways, I'm sure there are more good examples of unresolved teasers that I've either never known of or simply aren't coming to mind right now. I'll add them as I think of them, and, of course, if you know of any that I've omitted, please let me know in the comments!
Hope you enjoyed!
Phillip
UPDATE (3/9/2018):
So, after 2 and a half years they actually followed through on the "Trial of the Flash" storyline! I guess you can count this teaser as officially resolved. I'm just going to leave it down here for the sake of... I don't know, posterity?
Barry behind bars?
Is there still a chance of this teaser being resolved? Maybe, but I doubt it at this point. Some people say that it's a reference to the "Trial of the Flash" storyline from the comics, which very well may be true--though the shot isn't a recreation of any particular famous cover or anything like that (as far as I know). I guess we'll see if they ever adapt that particular storyline, but I think it's much more likely that this ends up as just another unresolved teaser.
