If you spent any time on Tumblr or YouTube around 2015, you probably remember the chaos. It was a specific kind of digital fever dream. One day you’re watching a show about magical space rocks, and the next, your dashboard is screaming that a chubby, pun-loving skeleton from an indie RPG is actually a dead, decomposed version of a cartoon boy.
The Sans is Steven Universe theory is arguably the most famous (or infamous) "crack theory" in the history of modern fandom.
It sounds ridiculous. Honestly, it is ridiculous. But to understand why people genuinely believed—or at least loved to argue about—the idea that Sans is Steven Universe, you have to look at the weirdly overlapping DNA of Undertale and Steven Universe. It wasn't just a random guess. It was a perfect storm of timing, visual similarities, and a very specific "Song That Might Play When You Fight Sans."
Why Did People Actually Think Sans Was Steven?
It started with a YouTube video.
In 2016, The Game Theorists (led by MatPat) released a video titled "Sans's SECRET Identity!" that basically lit the internet on fire. The core premise relied on a few key "coincidences." First, there’s the physical design. Sans is short, stout, and wears a blue hoodie. Steven Universe is short, stout, and... well, he wears a red shirt, but the body shapes are undeniably similar.
Then there’s the biological "evidence." Sans is a skeleton. Steven is a human-gem hybrid. If Steven were to die and rot away, what would be left? A skeleton. Specifically, a skeleton that might still have a glowing gem embedded in its form—which theorists linked to Sans’s glowing blue eye during the Judgement Hall fight.
It’s a stretch. A massive one.
But fans pointed to Toby Fox’s history. Before Undertale, Toby Fox was famous in the Homestuck community and for his EarthBound Halloween Hack. He was known for deep, meta-narratives and inter-textual references. People assumed that if anyone was going to hide a cross-media secret, it would be him.
💡 You might also like: Swamp Attack: Why This Weirdly Addictive Game Still Slays After All These Years
The "S.A.N.S." Acronym and the Letter
The theory got even more granular. Some fans claimed "Sans" was actually an acronym standing for "Steven After Not Surviving."
It’s the kind of logic that only makes sense at 3:00 AM after four energy drinks.
There was also a lot of talk about the "basement" in Undertale. In Sans and Papyrus’s house, there’s a locked room. Inside, you find a photo of three people with the message "don't forget." You also find a strange machine hidden under a curtain. Because Steven Universe involves a lot of warp pads and high-tech Gem machinery, fans leaped to the conclusion that this was Steven’s way of traveling between universes.
The Rebecca Sugar and Toby Fox Connection
One reason this theory gained so much traction is that the creators are actually friends. They respect each other's work.
Toby Fox actually composed music for Steven Universe. He contributed the track "Signs of Love" for the Steven Universe crossover with OK K.O.! Let's Be Heroes.
Because of this professional crossover, the "Sans is Steven Universe" crowd felt vindicated. If they’re working together, surely they’ve swapped characters!
Except, that’s not really how copyright works. Or storytelling.
Rebecca Sugar’s world is built on a foundation of queer identity, trauma, and healing. Toby Fox’s world is a subversion of RPG tropes and the morality of "grinding" in video games. While both deal with the power of kindness (Mercy vs. Pacifism), their internal logics are wildly different.
✨ Don't miss: Finding the Best Smoothies Echoes of Wisdom Players Actually Use
Steven’s powers come from his organic-gem physiology. Sans’s powers—his "shortcuts," his Gaster Blasters, and his manipulation of gravity—feel much more tied to the specific "coding" of the Undertale world.
Dealing With the Backlash and the Memes
Not everyone was a fan of the theory. In fact, most people hated it.
The Undertale fandom and the Steven Universe fandom were both at their peak intensity in the mid-2010s. When you mix two of the most protective fanbases on the internet, things get messy.
Critics pointed out the obvious:
- Sans has a brother, Papyrus. Steven is an only child.
- Sans bleeds (maybe? or is it ketchup?) when he dies. Steven’s skeleton wouldn't do that.
- The timelines don't match. Undertale takes place long after a war between humans and monsters. Steven Universe is a contemporary setting.
Eventually, the theory morphed from a genuine suggestion into a massive, multi-layered meme. You couldn't go into a comment section without seeing someone joke about "Steven After Not Surviving." It became a shorthand for "over-analyzing a series until it loses all meaning."
The True Identity of Sans (As Far As We Know)
If Sans isn't Steven, who is he?
The most grounded theories within the Undertale community actually point toward W.D. Gaster. Gaster was the former Royal Scientist who "fell into his creation" and was shattered across time and space.
The evidence for Sans being related to Gaster is much stronger:
- Sans uses weapons called "Gaster Blasters."
- Sans has a secret lab with blueprints written in symbols (likely Wingdings, Gaster’s font).
- Sans has a deep understanding of timelines and "SAVE" states, things a scientist would study.
Compared to the Gaster connection, the idea that Sans is Steven Universe feels like a fun, weird relic of a specific era of internet culture. It was a time when we wanted everything to be connected. We wanted a "multiverse" before Marvel made the concept exhausted and mainstream.
Why the Theory Still Matters Today
It's easy to laugh at it now.
But the "Sans is Steven" era represents a peak moment of collective creativity. It showed how much people cared about these characters. They wanted Steven’s story to continue, even in death. They wanted Sans to have a tragic, human backstory that explained his nihilism.
Even today, with Deltarune releasing in chapters, people are still looking for Sans’s origins. Is he from the Deltarune world originally? Did he "cross over" into Undertale?
The mystery is part of the appeal.
If we knew exactly where Sans came from, he wouldn't be Sans. He’s defined by his laziness, his secrets, and his refusal to give the player a straight answer. Whether he’s a skeleton from the Underground or a dead kid from Beach City, he remains the most iconic character of the indie game boom.
How to Navigate Fandom Theories Without Losing Your Mind
If you're diving into the world of lore hunting, keep these "sanity checks" in mind. They’ll help you distinguish between a cool hidden detail and a total reach.
- Check the Creator’s Intent: Does the theory align with the themes the author usually explores? Toby Fox likes meta-commentary; Rebecca Sugar likes emotional growth. Sans being Steven doesn't really serve either of those themes.
- Follow the "Legal" Trail: Characters are intellectual property. Unless there's a formal partnership (like Fortnite crossovers), it's highly unlikely one major IP is secretly a character from another.
- Look for In-Engine Evidence: In Undertale, look at the sprites and the dialogue files. Theories built on "vibes" are fun but usually fall apart under a data mine.
- Enjoy the "What If": You don't have to believe a theory to enjoy the fan art and stories that come from it. Some of the best AU (Alternate Universe) content came from the Sans/Steven crossover era.
The internet is always going to try to connect the dots. Sometimes those dots form a beautiful picture. Other times, they just lead you to a skeleton in a blue hoodie telling you a bad joke about "ketchup." Both are fine.
Next time you see a wild theory on your feed, remember Sans is Steven Universe. Remember how convinced people were. Then, take a breath, and maybe just enjoy the show for what it is.