Undertale Secrets & Cheats: Complete Guide to Every Hidden Password, Glitch, and Developer Room

Undertale hides a staggering amount of content behind specific conditions, obscure inputs, and timed triggers most players never stumble upon naturally. The fastest way in: name your character one of roughly 30 special strings at the start, manipulate the fun value in the game’s data files to spawn Gaster’s followers, or set your system clock to October 10th at 8 PM to trigger the So Sorry encounter. This guide catalogs every secret, password, glitch, and hidden item with exact steps — so you don’t spend three hours in Snowdin wondering why nothing is happening.

Note: all information verified against Undertale version 1.001 (PC). Most secrets carry over to Switch, PS4, and PS Vita versions, with the exception of file-editing tricks that require direct access to the game’s data folder.

Top 5 Secrets Worth Finding Before Anything Else

If you only care about the highlights, these five discoveries pay off the most in terms of lore, items, and sheer “wait, what?” moments.

• Name yourself “Chara” — triggers a unique reaction and unlocks a subtle narrative layer about the game’s true protagonist.
• Name yourself “Frisk” — activates Hard Mode for Chapter 1. Enemy spawn rates increase and dialogue shifts. Hard Mode ends abruptly after the Ruins, which is itself part of the joke.
• Developer’s Room in Snowdin — accessible after dodging every name in the credits sequence. One of the most complete easter eggs in any indie game.
• Dog Residue money loop — technically the closest thing Undertale has to an infinite gold cheat, and it works on every route.
• Gaster’s Followers via fun value 66 — these NPCs only appear under one specific condition and reference lore the game never fully explains anywhere else.

All Secret Name Passwords and What They Do

When you name your fallen human at the start of the game, certain strings trigger custom dialogue from a mysterious voice — or, in Frisk’s case, change the game mode entirely. These aren’t cosmetic. Several names alter the encounter’s tone in ways that recontextualize the story before you’ve even taken a step.

A couple of practical notes: “Papyru” — not “Papyrus” — is the one that triggers his response. Typing the full name produces no special reaction. Similarly, “Gaster” as a name doesn’t introduce any Gaster-specific content beyond the reset; his actual secrets require other methods entirely.

Cheats and Glitches That Actually Work

Undertale isn’t a game built around cheat codes in the traditional sense. No console commands, no konami code. What it does have: a handful of exploitable mechanics and one file-edit that the community has stress-tested extensively. These all function in version 1.001 on PC; the Dog Residue loop works on console too.

The Dog Residue Gold Loop

This is the only repeatable money exploit in the game, and it requires zero file editing. Here’s the exact sequence:

1. Obtain Dog Residue from the Snowdin Shopkeeper (it’s in the item list, not a drop).
2. Use Dog Residue from your inventory. This fills every remaining inventory slot with additional Dog Residue and occasionally Dog Salad.
3. Take your stack to the Tem Shop in Temmie Village.
4. Sell everything except one Dog Residue.
5. Use that remaining Residue to refill your inventory again. Repeat.

Dog Salad sells for more than Residue, so don’t burn through it carelessly. The loop is slow, but there’s no ceiling — useful if you want to buy Temmie Armor, which costs 9,999G and is legitimately expensive otherwise.

The Punch Card / Menu Buffer Glitch

This one is beloved by speedrunners. The Nice Cream Guy in Waterfall gives you a Punch Card item. When a cutscene triggers, if you open and close the Punch Card at the exact frame the cutscene starts, the game advances one pixel’s worth of movement per frame instead of locking you into the full sequence. In practice, you open the menu, click a directional arrow, and alternate — pixel by pixel — through a trigger zone. The cutscene plays out truncated, and you walk free early.

It’s not a skip so much as a compression. Some cutscenes are reduced to a second or two. The timing window is tight, and it takes practice, but it’s consistent once you have it down.

Spawning Glyde in Snowdin

Glyde is a secret enemy that only appears under one condition: visit the Mysterious Door room in Snowdin Forest and wander around in that area for at least two full minutes without engaging or killing any Snowdin monsters. On a Pacifist Route, Glyde will eventually appear to pick a fight. He’s not part of the kill count and missing him doesn’t affect any ending.

Worth noting: he appears specifically because the game tracks whether you’ve been idle in that room long enough. The encounter exists as a kind of punishment for dawdling — which is very on-brand for Undertale.

Editing the Fun Value (PC Only)

In Undertale’s save files, a hidden variable called “fun” is randomly assigned a value between 1 and 100 each time you load the game. Most values do nothing visible. But specific numbers unlock specific content. To set it manually, locate the undertale.ini file in your save folder (on PC: %localappdata%/undertale/), open it in a text editor, and change the fun= line to your target number before launching.

Key fun values and what they unlock:

• fun = 66 — Spawns Gaster’s Followers in Hotland and Waterfall. These NPCs discuss W.D. Gaster in fragmented, unsettling monologues.
• fun = 62 — A telephone in Waterfall plays an unusual garbled sound, believed to be Gaster-adjacent.
• fun = 65 — A mysterious figure appears briefly in a random room and vanishes.

Fair warning: editing save files on PC is straightforward, but back up your save folder first. The game won’t corrupt from a fun-value edit alone, but it’s easy to accidentally overwrite a Pacifist save.

Hidden Items and Locations Worth Tracking Down

Some of these require you to be on a specific route. Others just reward curiosity. The Developer’s Room in particular is one of those secrets that most players miss even on second playthroughs, because the entry condition isn’t explained anywhere in the game itself.

The Developer’s Room (Snowdin)

There’s a large door in a cave in Snowdin that appears completely unopenable. It is — but only after you complete the game’s credits sequence while dodging every single falling name. Once you successfully avoid all the credits, the door becomes accessible on your next playthrough visit. Inside: developer notes, character commentary, and references that serve as some of the most direct communication Toby Fox has put into the game itself.

Temmie Village

Temmie Village is easy to miss because reaching it requires a specific action most players don’t think to try. In Waterfall’s dark mushroom section, light all the mushrooms by walking into them. Then follow the southward path that opens up — it leads directly into Temmie Village. You’ll find a Temmie shopkeeper who sells items and, eventually, Temmie Armor after you pay for her college education (yes, really).

Sans’ Room in Snowdin

To unlock this, you need to reach New Home and complete a Pacifist Route up to the golden room conversation with Sans. Save before speaking to him, then talk to him and exit the game. Reload and repeat the process two to three more times. On one of those cycles, Sans will hand over a key. Return to Snowdin — his room is accessible from the back of his house and contains hand-drawn notes, observations about alternate timelines, and what many players consider the most affecting piece of environmental storytelling in the game.

Sans’ Hot Dog Variants

Sans sells hot dogs from a cart in Hotland. There are four versions, and each requires a specific condition:

• Hot Dog — Buy directly from Sans.
• Hot Cat — Buy a second one from Sans in the same visit.
• Head Dog — Buy a Hot Dog when your inventory is completely full. Sans stacks it on your head instead.
• Hush Puppy — Buy “Hot Dog…?” from Sans, then place it in front of the final door at MTT Resort. You lose the Hot Dog, but receive a Hush Puppy instead.

Gaster’s Followers

As covered in the fun value section, setting fun to 66 spawns three unique NPCs. The first appears in Hotland and claims to be unable to describe Gaster. The second appears in Waterfall and describes forgetting what Gaster looked like. The third is a grey-colored creature that just stares. None of them give items. All of them are worth seeing at least once, because the Gaster lore has never been officially explained, and these encounters are the primary source material for an enormous amount of fan theory.

Genocide Route Exclusives — What Only Appears When You’re Killing Everything

A few secrets are locked specifically to Genocide — and this matters more than it sounds, because Genocide has strict requirements. You must kill every monster in each region before progressing, and encounter counts are tracked per area. Miss even one, and you won’t trigger the route’s unique content. So Sorry, listed below, is actually one of the few Genocide-adjacent encounters that players frequently miss because of its date-dependent condition.

So Sorry (Art Club Room, Hotland)

So Sorry is a secret boss found in the Art Club Room in Hotland. Three conditions must all be true simultaneously:

1. Read the sign posted at the Art Club Room entrance.
2. Your system clock must be set to October 10th at 8:00 PM (or later that evening).
3. You must have reached the MTT Resort before entering.

Some sources cite this as requiring a specific route. Community testing suggests So Sorry can appear outside of strict Genocide, but the encounter is most reliably documented on Genocide runs. If you’re attempting it outside of that context, confirm the date/time manipulation is active and that you’ve reached the Resort first.

On PC, changing your system clock before launching the game is the most reliable method. The encounter resets the next time you load under normal date conditions, so you can’t accidentally lock yourself into anything.

Unique Genocide Dialogue and Route Markers

Several characters have Genocide-exclusive dialogue that counts as “secrets” in the broader sense — they’re missable and most players never see them. Sans’ judgment monologue is the most famous, but Papyrus’ shortened fight, Undyne the Undying’s transformation trigger, and the game’s final Genocide confrontation all contain moments that only appear once, in one playthrough, and cannot be revisited without resetting your save data entirely.

One edge case worth flagging: after completing a Genocide Route, the game’s data carries a persistent flag even after you “restart.” A returning character in a subsequent Pacifist playthrough will call this out directly — which is itself a secret of sorts, since most players don’t expect the game to remember what they did.

Frequently Asked Questions

Does naming yourself “Gaster” unlock any Gaster content?

No. Naming yourself Gaster simply resets the intro sequence and starts it again. All actual Gaster content — followers, phone calls, the figure in the hallway — requires specific fun values set via the save file on PC.

Can you access the Developer’s Room on console?

Yes. The credits-dodging method works on Switch, PS4, and PS Vita without any file editing. The door in Snowdin becomes accessible the same way regardless of platform.

Does the Dog Residue loop work on Genocide?

Technically yes, but there’s almost no reason to use it on Genocide — you can’t shop at Temmie Village on that route, and most purchase options become irrelevant. The loop is most useful on Neutral or Pacifist runs when chasing Temmie Armor.

Is Hard Mode (Frisk name) worth playing?

It’s a curiosity more than a full experience. Hard Mode ends abruptly after Toriel’s boss fight with a “too be continued” message — it was never finished. The increased spawn density and altered dialogue in the Ruins are genuinely interesting, but don’t go in expecting a complete alternate route.

Can completing Genocide ruin a Pacifist playthrough permanently?

The persistent flag after Genocide affects one specific moment in a subsequent Pacifist run — a character will acknowledge what you did. This is intentional. You can still achieve the Pacifist ending, but the game does not fully let you pretend the Genocide run didn’t happen.

Between the name passwords, fun value manipulation, the Dog Residue loop, and route-locked encounters, Undertale packs more conditional secrets into seven hours than most games manage across a full campaign. The Developer’s Room alone is worth a complete run just to see — and if you’ve only ever played through once on Pacifist, Gaster’s followers and the Genocide-exclusive dialogue represent an almost entirely different emotional register. Start with the names, work toward Sans’ room, and set aside an evening for the fun value experiments. There’s more here than the game ever advertises.