Buffy the Vampire Slayer followed Buffy Summer and her Scooby gang as they protected Sunnydale from vampires, demons, and any other supernatural threat that came up. The first couple of seasons featured mostly stand-alone stories, or "vampire of the week" as they were dubbed. It also adopted ending some episodes with little twists or questions, which was a popular storytelling device in the '90s on sci-fi and fantasy shows like The X-Files.

One such episode was season one’s "Out of Mind, Out of Sight." Buffy and friends took on an invisible girl out for revenge against the popular kids. Its intriguing twist ending still has audiences wondering about it years later. Some fans have even created their own little head cannons to fill in the blanks and tie it to another Buffy storyline from season four—where it would have fit perfectly.

The School for Invisible Assassins Had a Lot of Potential

"Out of Mind, Out of Sight" features guest star Clea Duvall as Marcie Ross, a student who has turned invisible from feeling ignored and unseen. As Marcie taunts Cordelia, who is one of the people she blames for her invisibility, viewers see sepia-toned flashbacks of the numerous times Marcie tried to engage with her fellow students and teachers, only to be ignored. The time when Marcie tried to join a conversation with Cordelia and her friends, but they ignored her and stole her jokes as their own. The time in class when the teacher called on everyone but her, so she just stopped raising her hand. The scenes are surprisingly affecting due to Clea Duvall's performance.

With every one of Marcie's attacks, she leaves a message hinting at her endgame. The first victim is Mitch, Cordelia’s date for the May Queen dance. She beats him with a baseball bat, and spray paints "Look" on the locker doors. Her next attack was on their English teacher who was going to help Cordelia with her school work. Marcie puts a plastic bag over her head and suffocates her. Cordelia comes in time to save Ms. Miller, just as Marcie writes "Listen" on the blackboard. Her final message was "Learn," and she planned to disfigure Cordelia’s face as a lesson to the pretty and the popular, saying that everyone would remember her new face.

Giles proposes that reality is shaped by perception, and the mystical energy from the Hellmouth gave it the extra boost it needed to actually turn the girl invisible. The Scooby gang began their investigation sympathetically as this was something that was done to Marcie Ross, as opposed to something she did to herself. As the story progresses and Marcie turns out to be a psychopath, Buffy doesn't empathize as much in the final battle. It is a classic Buffy story, taking the insecurities and challenges of adolescence and putting them in the context of the supernatural. The episode is mostly well-received, even though it doesn't have much bearing on the arching story of the master and his impending escape from hell.

In the end, Marcie is carted away by two FBI Agents and brought to a classroom full of seemingly empty chairs. Marcie sits down and opens her textbook to a page that reads "Assassination and Infiltration." The implication is that the FBI is aware of the supernatural and has departments dedicated to finding ways to use it to their advantage. The idea of a Buffyverse X-Files-type unit of the FBI had a lot of potential for a fun and interesting storyline, but it was disappointingly never revisited on the series—even though it fit in perfectly in season four.

The Initiative Would Have Been the Perfect Place to Bring It Back

In the fourth season of Buffy the Vampire Slayer, the show introduces a new element to it. The Initiative was a secret branch of the military that hunted demons, monsters, and the forces of darkness. Humans trained to hunt and fight demons would patrol the streets to capture dangerous creatures. Some they would dissect, others they would de-fang—like Spike, in whom they plant a neural chip that prevents him from hurting humans. One of the commandos was Riley Finn, Buffy’s new boyfriend. Even after the Sunnydale location was dismantled because of Professor Walsh’s questionable experiments, The Initiative still existed. Viewers saw them again in season five when Riley needed to have an operation for a heart issue.

The Initiative would’ve been a perfect place to fold in the Invisible Assassins storyline. In fact, many fans have created similar stories in their minds, saying that the classroom was somehow connected to the initiative and the students are just at a different facility. While these sorts of dropped storylines are fairly commonplace in genre television, some ideas stick with audiences long after the episode is over. Even a little drop-in about a mysterious locked-room assassination on the news would’ve been a fun payoff from the episode.

The show never revisited the school for invisible children, but it did have a callback to the affliction of the ignored and unseen turning invisible. In season seven's "Storyteller," Buffy sees a young girl beginning to fade away in the hallway, and she goes and talks to her. When the shy girl doesn’t reappear right away, Buffy slaps her back into visibility. The girl felt seen at that moment and didn’t become invisible. There was a host of other Hellmouth-energy-induced strangeness in the school caused by a seal to the underworld that had been activated by Andrew murdering Jonathan at The First's behest.

"Out of Mind, Out of Sight" Wasn't the Only Dropped Teaser Ending

There were a few dropped teaser endings from Buffy the Vampire Slayer that left fans wondering what happened. Season one's "Teacher's Pet" is about a new female teacher at the school who takes a special interest in Xander. She turns out to be a life-sized Praying Mantis who only appears human. She prays on virgin male students, looking for a mate. She seduces Xander along with another student, holding them in her dungeon. Buffy and the team rescue them before she can bite their heads off. One of the final shots of the episode was a nest of her mantis eggs that began to hatch.

Season two's "Go Fish" didn't expand on what exactly happened to the swim team members that turned into creatures from the Blue Lagoon. Their coach was dosing them with some experimental steroids to help them swim faster, but those exposed to too much of the drugs turned into gill monsters. At the end of the episode, they run off into the ocean. They are presumably just out there in the ocean doing who knows what. While they were at Sunnydale High, they ate the school nurse and their coach, so it's hard to imagine they're not getting into trouble wherever they swam off.

"I'm very excited that we're gonna learn more about the journey of Buffy Summers and how she saves the world because I think the world needs her. So I'm gonna do my part by doing nothing right now."

With Sarah Michelle Gellar attached to a Buffy the Vampire Slayer reboot that is in the works, there is always a possibility that they will tie in or callback to storylines from the original series. There is very little known about the reboot thus far. So far no other cast members are attached, and James Marsters, who played Spike has said that he's excited about the prospect of the show, but the best thing he can do about it is to keep his mouth shut.

"I'm very excited that we're gonna learn more about the journey of Buffy Summers and how she saves the world because I think the world needs her," Marsters said in an Instagram live. "So I'm gonna do my part by doing nothing right now."

Another question about the reboot is how it will factor into the comic books that have continued Buffy's story. Everyone involved is keeping details close to the vest for now, so fans will just have to wait and see as the highly-anticipated project develops.