For example, two characters not seen since Breaking Bad's second season make an unexpected reappearance in the penultimate episode. When he sees his former friends Gretchen and Elliott Schwartz dissing him in a TV interview, Walter White gets the motivation he needs to finally come out of hiding, setting up the shocking events of the series finale.

It's one of those moments that made us go "Ohhh, so that's why they did that thing four seasons ago! It all comes together!" And we were completely wrong about that, because the writers weren't even planning to bring those characters back -- until they heard from Kevin Cordasco.

Hollywood Reporter
Pictured here with the cast, cosplaying as Skinny Pete.

That's the name of the 16-year-old with neuroblastoma whom showrunner Vince Gilligan called "our wonderful, number one fan." When Gilligan visited Cordasco during his final months, he asked him if there was anything he felt the show needed. The fan replied, "I want to know more about Gretchen and Elliott. I want to know more about Walt's backstory with them. I want to know what happened."

Gilligan hadn't thought about incorporating the characters into the plot, but Cordasco's comment gave him pause. He'd been stumped trying to figure out how to get Walt out of hiding, but as he mulled over Cordasco's suggestion, he discovered that the answer indeed lay with the Schwartzes. Writer/director Peter Gould raves about the choice, gushing, "Walt seems to change his mind there. He's all ready to get caught, and then he sees the video ..." This is made even more impressive by the fact that, if more shows incorporated ideas from teenage fans, it probably wouldn't end so well.

AMC, HBO
Unless that already happened and we just didn't notice.

How big a fan was this kid, exactly? Let's put it this way: When Gilligan, Breaking Bad's creator himself, offered to tell him how the show ended, Cordasco was like "Hey, no spoilers, man." That's dedication.

Of course, there was no such thing as the cow level -- it was just one of those wacky random jokes the Internet loves to this day ("cow level" was the "the cake is a lie" of its era). Until, that is, Diablo's creators at Blizzard saw the rumor and said "What the f**k is wrong with these people?" followed by "We should make that a real thing." The first thing they did was insert an Easter egg in StarCraft subtly informing players of the level's nonexistence (the "There is no cow level" cheat code). But then, on April 1, 1999, the following image was released without commentary as Blizzard's Screenshot of the Week:

Blizzard Entertainment
Even back then, games paraded out poorly covered females, exposing their massive udders.

Cue a million confused nerds shouting "WHAT DOES IT MEAN?!" Some were convinced that it was a dirty April Fool's prank, while others kept the faith. The true believers were rewarded: Blizzard went ahead and included a secret cow level in Diablo II, and now you can totally decimate some bovine ass if you follow the instructions on their website (if you're into that sort of thing).

And later, when some fans began clamoring for a Secret Pony Level in Diablo III, most likely in jest (we would hope), they freaking did it again:

Blizzard Entertainment
Horns, hooves, homicide ... they're like any other demon, only creepier.

And here's how they looked in the first movie a decade later:

Paramount Pictures
He should have kept the bangs.

Naturally, fans wanted to know why an entire race had suddenly developed hideous ridges on their foreheads, but they were unlikely to get an answer, because everyone already knew the real reason -- namely, that the entire original series was shot for like five bucks (most of which went to strengthening William Shatner's man girdle), while the movies and subsequent shows actually had a budget to spend on makeup and prosthetics to make the aliens look like aliens.

And so it was left to the fans to debate a slew of evolutionary theories in the ensuing decade that might explain why some Klingons look like humans and some look like Italian hobbits who got a face full of acid. Some claimed getting freaky with the local species on other planets was to blame, while others insisted that it was simply natural selection in those new environments. The prevailing theory was a genetic mutation somewhere along the line, and it was this theory at which series creator Gene Roddenberry apparently shrugged his shoulders and said, "Good enough."

Larry D. Moore
"Hell, those spinoff series are all just fan fiction anyway."

Fans first got to hear their own words repeated on the screen in a 1996 episode of Deep Space Nine, when the contemporary characters see some of the original series Klingons via time travel and ask: "What happened? Some kind of genetic engineering? A viral mutation?" But the money shot didn't come until Season 4 of Enterprise, in which it's finally explained that the Klingons had in fact dabbled with genetic engineering, but being a race better suited to killing rather than sciencing, it didn't go so well. Some died, while others who mutated temporarily lost their beautiful, beautiful ridges.

As a result, something that fans had endlessly argued about during conventions became an official part of the fictional Star Trek universe. It turns out that sometimes, when you stare into the abyss of Trekkie fandom, it stares back into you.

Readers had some questions, namely "Huh? When? Also, why? Also, huh?" Marvel was content to leave them puzzled, but they weren't counting on J.R. Fettinger. Known within the fandom as Madgoblin, Fettinger runs a fan site called Spidey Kicks Butt, where he writes about Spider-Man kicking butt. Over the course of a 12,000-word essay, Fettinger explains how he pinpointed exactly when and why the affair must have taken place, putting a lot more effort into making sense of this mess than the actual writers.

And he achieved it: He points out the 1967 issue when Norman Osborn, temporarily reformed and amnesiac, saves Gwen and her father from the villainous Kingpin. Add that to the fact that Gwen had banished Peter from her life at this point, believing him to be a dad-hitting scoundrel, and suddenly it's a lot easier to buy that they both succumbed to a moment of weakness in their shared vulnerability. In other words, it was just kind of a weird time in their lives.

Marvel
Also, no one could resist those sexy cornrows.

He also points to comments Stacy had made, such as having mysteriously gone to see Osborn "on another matter," because holy s**t, this dude is seriously invested in the sex lives of ink people.

After Marvel came across the essay, instead of immediately filing a restraining order, they approved the theory as the official explanation: It now appears on the Marvel website and in several editions of the Official Handbook of the Marvel Universe. Keep in mind that comic fans do this all the time -- there's a 10-part treatise somewhere out there about why Batman's left boot was colored yellow for one panel in 1952. Getting your idea not just acknowledged but incorporated by the company you're obsessed with is the definition of nerd heaven.

One of the most notorious of these rumors is known as the Living Forest fatality. The story went that sometimes after finishing an opponent in the Living Forest stage of Mortal Kombat II they would be thrown to a gnashing death at the jaws of a demon tree. Everyone knew someone who swore they saw another player do it at Chuck E. Cheese's, but couldn't remember the exact button combination.

Chris McCullough

Sure, it's obviously bullshit, but if upon reading the description you didn't just say "that sounds metal as hell," you were raised wrong, and also you disagree with Mortal Kombat 9 lead designer John Edwards. As he put it, "The fans imagined and made rumors up of things that weren't actually there for stage fatalities. In a lot of cases, we fed off of those old-school rumors and turned them into realities this time around." That includes -- yes, children -- the Living Forest fatality. You can now totally turn your opponent into a juicy snack for a satanic sequoia:

Warner Bros.
Nom nom kom.

Another new addition was the character Skarlet, a rumored (but untrue) glitch in Mortal Kombat II that turned the female ninja character's costume red. She's now a distinct downloadable character, complete with a history matching the lore made up by fans, because writing character bios is hard, you guys. Why not let the unwashed masses do it for free?

Warner Bros.
So go call that friend from middle school and say, "See? She exists. Now you have to eat a poo."

And yet, it came from the least likely place to find useful and non-terrifying ideas: the fan art community. Yes, the refuge of frustrated comic book artists at best, full-on cartoon pornographers at worst.

The plasmid started life as a simple piece of fan art created by graphic designer by day/obsessive fanboy by night Joe Trinder. After being posted on the Irrational Games message board, the fan art found its way to Reddit, where it earned 9,000 positive votes due to its indisputable awesomeness (and 7,000 negative ones, because Reddit).

Joe Trinder
Reddit hates alliteration, ever since the 2012 incident.

The image was eventually seen by BioShock creator Ken Levine, who was so in love with it that he couldn't even discuss it without developing a spontaneous case of Tourette's: "I just saw the piece of art and I was like, 'holy s**t, this is f*****g great,' then talked to the legal department to see if we could use this, because we love it."

He contacted Trinder within a day to buy his design.

Irrational Games
He broke into Trinder's home and pushed a note to him under the bathroom door.

Trinder figured it would be a case where you just see his poster in the background for a second, so even he was surprised to find out that the ability he made up became a central part of the game. Meanwhile, Levine admits he "goes on DeviantArt all the time," just looking for people to shower with his sticky, sticky money. What we're saying is, don't be ashamed of jerking off to Internet nerd porn: Your heroes are most assuredly doing the same.

Manna is constantly having brilliantly stupid ideas over at Mannafesto and on Twitter.

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Related Reading: Sadly, the best fan theories are seldom adopted. But we'll always consider James Bond more of a code name than a man. And the Matrix really WOULD be better if it had been revealed that Neo was a machine. Of course, sometimes creators should just stay away from their fans. The marriages never end well.