With past villains like Zoom and Savitar, The Flash nearly created a cottage industry built on fan theories about who was under the masks. In Season 4, the CW drama has managed to craft equally engaging mysteries without relying on masks to hide identities, and in the case of the Mystery Girl (as she's come to be known), we know exactly what she looks like. We just have next-to-nothing to go on besides that, however, from a name to a motivation to anything else.
Perhaps due to that lack of information, Flash fans have been pretty active in theorizing about the potentially endless number of characters that Jessica Parker Kennedy may be portraying. Showrunner Todd Helbing recently claimed that none of the theories he's read online have been correct, so here, we're stepping outside the box to take on some theories that don't automatically assume Mystery Girl is Barry and Iris' direct offspring. First up, let's consider someone's offspring that we have actually laid eyes on before.
Obviously, I'm not going to pretend that Mystery Girl is, in reality, a toddler dressed up in an adult human costume that has the abilities to do all the adult human things that toddlers can't. But that concept is arguably only as inconceivable as Barry Allen traveling to the past and creating an entirely separate timeline for himself and everyone he knows. The Flashpoint timeline definitely exists, though, and it's the last known location of Sara Diggle, whose existence was replaced with that of John Diggle, Jr.
So what if the Flashpoint timeline remained unstable and got as horrible for everyone else as it was for Barry, leading to Sara's parents John and Lyla getting killed for one reason or another, leaving Sara to grow up miserable, afraid and in need of revenge. The metahuman situation was quite different in the Flashpoint timeline, so it's not exactly clear how Mystery Girl would have traveled back into another timeline's past events, but where there is a speedster (Wally) and a Cisco (billionaire jerk or not), there is a way.
Female Malcolm Thawne
Though The Flash's first big bad initially seemed to be Harrison Wells, fans later learned the person actually responsible for creating The Flash was Eobard Thawne, whose entire time-travel plan was formed to keep Barry Allen from ever becoming the Scarlet Speedster. (Spoilers: he failed.) But while viewers were introduced to Eobard's current-era ancestor Eddie, there are many other Thawnes from the comics that haven't been touched on at all. Such as Malcolm Thawne, Barry Allen's secret twin who was (rather illegally and haphazardly) given to far less virtuous family just after childbirth. Later in life, Malcolm learned of Barry and tracked him down, following him for a while, growing ever more jealous and hateful of this life that was taken from him.
While Mystery Girl's first pair of appearances seemed good-natured enough, her most recent cameo implied she may have more nefarious intentions than...bringing people coffee they ordered. So what if she's actually been following Barry around because she wonders about what life would have been like had she remained an Allen? Sure, she's not the same gender, and actress Jessica Parker Kennedy has a more diverse heritage and is also a few years older than Grant Gustin. But how badass would that change-up be? In the comics, Malcom's parents were petty criminals with a special blue-flame power that he later adopted in taking on the villainous persona Cobalt Blue. That villain is one that Flash fans have consistently been asking for, and this would be one of the wildest ways possible to make it work.
At this point, The Thinker is getting further and further from the single-man origin story that viewers saw earlier in Season 4. He is no longer just Clifford DeVoe performing instantaneous mental calculations in order to predict situational outcomes. (Hell, even Harry can do that now.) Currently, The Thinker is transporting his consciousness from one metahuman to another, gaining their various powers along the way. So what if Mystery Girl is actually The Thinker in the form of one of those alternate metas?
We did see her drawing symbols similar to the ones that Barry was drawing, which were also seen on DeVoe's washed-out Thinker-face. But how could Mystery Girl and The Thinker both exist within the same timeframe as two different entities? Take your pick. Perhaps this meta's powers include time travel, which could make her a future version of The Thinker who's setting things up for a specific outcome, similar to what DeVoe was seemingly doing before his body was too weakened. Alternately, Mystery Girl might have a full suite of meta powers that we're not familiar with yet, making her the ultimate host for The Thinker's brainpower.
A Speed Force Entity
Once Hunter Zolomon's Zoom was demonically transformed into the underused Black Flash, it seemed like The Flash's Speed Force had a better authority than those dreaded Time Wraiths to take down speedsters who don't follow the rules. But throughout the entirety of Season 4, the sentient Speed Force has been without an actual speedster inside of it, with Barry's replacement being a DNA-infused quark sphere. But what if the Speed Force has gotten wise to what Barry and Cisco did, and it sets forth a strange form of revenge by taking the form of Mystery Girl?
There are admittedly more questions than answers for this to be the case -- such as why Mystery Girl is interested in other characters beyond Barry -- but some things add up. Those weird symbols that Barry was drawing are assumed to be Speed Force-related, so if Mystery Girl is also drawing them, wouldn't that be a solid link? The fact that she seems to pop in and out of existence also hints at an otherworldly-ness. And even though the Speed Force has used Barry's dead familiars to entice him in the past, perhaps a new personality was needed as not to draw suspicions. Suspicions of what? Big...Speed Force...plans, of course.
Cisco And Gypsy's Kid
Immediately after Mystery Girl first showed up during Barry and iris' initial botched wedding, fans started theorizing that she was a future-based WestAllen descendant, but what if she's actually part of the future Ramon family tree? It's not completely out of the question that Cisco and his Earth-19 girlfriend Gypsy would have a kid one day, and that the kid would eventually find a way to go back in time to communicate with her father and his friends for some reason. It would definitely be a left-field reveal, but not one without clues leading viewers to such a conclusion.
Mystery Girl has that whole "spontaneously appearing wherever Team Flash members are" tactic down to a science, which hints at her possibly having the same kind of inter-dimensional vibing powers that Cisco and Gypsy have. (No clue if those things are genetically passed on or not.) She actually does look way more like Carlos Valdes and Jessica Camacho's hypothetical child than Grant Gustin and Candice Patton's. But the biggest piece of proof? Mystery Girl works at the coffee shop Jitters, which is exactly where a caffeine-craving Earth-19 citizen would want to work, since coffee beans are extinct in that dimension. Maybe Mystery Girl is so anxious all the time because she's not used to all the espresso.
The Flash will hopefully answer this question sooner than later, since our curiosity is making us a little...jittery. Watch the superhero action Tuesday nights on The CW at 8:00 p.m., with the next episode arriving in a few weeks. In the meantime, let us know what you guys think in the poll below, and head to our midseason premiere schedule to see what's yet to come.