Released in 2015, Undertale remains one of the best indie games in recent history. This friendly RPG was all about exploring the underground world of monsters and making choices on whether or not to befriend them or use violence to get what you want. The game also paid tribute to a wide array of classics such as Earthbound, and like those older games, it features a wide variety of secrets.
Undertale is, in fact, famous for its secrets, as there are an incredible number of them across the various different versions of the game on both PC and console. From hidden villages to mysterious scientists to ominous followers, let's now take a look at 10 secrets from Undertale that you may not have known about.
10 Temmie Village
First on our list is the isolated Temmie Village, a secret settlement of Temmie monsters hidden off the beaten path in the Waterfall region. It takes a bit of work to find this place, as you must walk down an invisible path to reach it. There are a few hints in the dialogue from other characters, but otherwise its up to you to make your way here.
Temmie Village is full of Temmies (naturally), each of whom have unique and humorous dialogue. The Tem Shop here is also the only place in the game that lets you sell items in your inventory. You can also eventually purchase the Tem Armor here - the best armor in the game.
9 Mad Mew Mew
Secret boss fights are always a neat secret to find, and Undertale has quite a few of them. For this fight, you'll need to own the Nintendo Switch copy of the game, and interact with a few things in Papyrus's house before uncovering the route to Mad Mew Mew.
The boss fight itself is tricky, as it introduces a new mechanic where the player's soul is split in two and you must move each half independently to the correct positions. You can't actually hurt Mad Mew Mew, and must instead survive long enough to spare her.
8 Shyren The Star
Upon entering Waterfall, players will be accosted by the unique monster, Shyren. To spare her, all you need to do is encourage her to follow her singing dreams, which unlocks the option to end the fight non-violently.
For players who want to do more, though, continuing to encourage Shyren sees her becoming bolder and more confident. Her attacks (or rather, her songs) become faster and harder to dodge, but you'll get to follow along as she eventually winds up performing on stage.
7 So Sorry
Not all of the secret boss characters in the game are console exclusive. Anyone with a copy, be it PC, Playstation, or Switch, can find this next entry. You'll need to find the Art Room in the Hotlands region which then leads the player to bump into this artist monster, kicking off the fight with So Sorry.
So Sorry has several "attacks" based around the monster clumsily trying to share their art. Sparing the creature leads to a series of humorous dialogue lines, whereas trying to kill them has its own set of equally amusing exchanges. Either way, this boss is still a fascinating find.
6 Hard Mode
For reasons that are explained at the end of a Pacifist playthrough of Undertale, the canonical name of the game's protagonist is Frisk. For those same reasons, naming your character Frisk at the start of the game could absolutely lead to some serious problems. It makes sense, then, that doing so unlocks the game's Hard Mode.
Hard Mode is pretty short, lasting only till the end of the Ruins section. New monsters, as well as monsters from later in the game, can be encountered here, and there are numerous changes to how other elements in the game world work as well. It's not for the faint of heart, although it is certainly an interesting experience for any who want a bit of a challenge.
5 Flowey The Stalker
The first character you'll meet in Undertale is Flowey the flower, a smiling little daisy that almost immediately tries to kill you. Flowey pops back up periodically throughout your game, commenting on your actions and how you've been playing. However, he actually shows up much more often than most people realize.
If players stop suddenly and then quickly backtrack, they may be able to catch a glimpse of this homicidal plant before it shrinks back into the ground. This explains how Flowey always seems to know where you are and what you've done - he's following you, which somehow makes his character even creepier than before.
4 The Dog's Room
This area is quite a challenge to reach, as it requires some serious skill to unlock. You'll need to complete the game on a Pacifist run, sparing every single monster in order to unlock the true credits. Then those credits will animate and start flying towards you. If you manage to dodge all of them, then restart the game, this small area in Snowdin will be available.
Inside is the Annoying Dog, which is generally accepted to be a metaphor for the game's creator, Toby Fox. Interacting with the dog and items around the room lead to some fourth wall breaking jokes and comments about the game, such as fixing bugs. It's a nice little Easter egg for anyone who wants to put in the effort.
The final secret boss on this list, Glyde can be encountered in roughly the same area as the Dog's room from the previous entry. You'll need to head to the room with the locked door in Snowdin, and then consistently keep moving in that area. Eventually, you'll encounter Glyde.
This monster is extremely arrogant and repeatedly makes references to its supposed coolness. Defeating it can be done either in the standard way of attacking it until it dies, or by applauding twice, then ignoring it. The latter option will eventually cause Glyde to leave, looking for praise elsewhere.
2 Sans's Room
This next entry can only be obtained during a Pacifist route, and can take a long time to pay off. You'll need to play nearly the entire game, to the point where you reach the hall where Sans judges you for everything you've done. Once the encounter is over, you'll need to reload the game and do it again - and then again.
Repeating the process enough times leads Sans to give you the key to his room back in Snowdin Village. You can return to the area, then enter to find a few mysterious hints at Sans's past. There's nothing definitive there, but its does help further some of the stranger conundrums of the character.
Finally, what may be (somewhat ironically) one of the most well known secrets of Undertale is the existence of WD Gaster. This character is only very rarely mentioned, as the characters associated with him show up randomly and talk about him in evasive, uncertain dialogue.
You can actually find him in the game as well, although he appears even more rarely than the characters that mention him. When he does show up, he can be found by going through a nondescript door in Waterfall, and he disappears the moment you attempt to interact with him, making WD Gaster the most mysterious secret in a game chock full of secrets.