* To know more, see Undertale Wiki's page:

"Beware of the man who speaks in hands."
River Person

W. D. Gaster was the royal scientist before falling into his creation. Presumably, Entry Number 17 (as it talks about experiments) is written by Dr. Gaster which mean he speaks in the Wingdings font. Because of this, people generally take the initials W. D. to stand for Wingdings and that he is a skeleton. His text, what little there is, is in all caps similar to Papyrus. They are the Forgotten Scientist in Undertale and remains unswapped in the Team Switched version of Underswap'


Gaster was a royal scientist before Alphys. He fell into his own creation, generally assumed to be the Core as it is the only thing known for certain that he created. He was then shattered through time and space, as one of his followers states. When exactly this happened is unknown but it's said to have been a 'long time' before Alphys was hired.

Finding Gaster

Originally the only way of encountering 'mystery man' (the sprite which is confirmed to be W.D. Gaster by the official Tarot cards set) was editing the FUN factor to 66. Post an update, the only action required to trigger the corridor is to rest 66 time. It appears in the Waterfall area between the crystallized cheese room and San's telescope. Whether or not the door appears in the corridor is random. Apon interacting with him, he becomes surprised and then disappears.

Gaster's stats were found by data mining the game's data, and they state: 666,666 HP, 66,666 ATK and DEF.

Entry number seventeen

By hacking the game and changing your location to a certain room that does not appear on the map, the following text appears written in Wingdings 1:


For more information on W. D. Gaster, look here.

📬︎📬︎📬︎📬︎❄︎☟︎✋︎💧︎ ❄︎✋︎💣︎☜︎☹︎✋︎☠︎☜︎ 💧︎☜︎☜︎💣︎💧︎📬︎📬︎📬︎📬︎🕆︎☠︎✋︎✈︎🕆︎☜︎📬︎📬︎📬︎📬︎

👌︎ ☜︎ 🕈︎ ✌︎ ☼︎ ☜︎   ⚐︎ ☞︎  ❄︎ ☟︎ ☜︎  💣︎ ✌︎ ☠︎  🕈︎ ☟︎ ⚐︎  💧︎ 🏱︎ ☜︎ ✌︎ 😐︎ 💧︎  ✋︎ ☠︎  ☟︎ ✌︎ ☠︎ 👎︎ 💧︎📬︎

Common AU canons

Skeleton family

Due to him speaking in a font different to 8-bit operator and his name seeming to connect to his font, he is assumed to be a skeleton and hence somehow connected to the skeleton brothers. This is reinforced by Sans's Gaster Blasters.

  • Due to the expected age difference, he is usually considered a father/creator of the brothers though he is sometimes another brother.
  • Other times he is a being that got split in two; one half becoming Sans, the other Papyrus with the empty shell being the 'mystery man' seen in the Waterfall room. (For those familiar with Pokémon, it's close to the Gen 5 legendaries (Sans = Reshiram, Papyrus = Zekrom, remains of Gaster = Kyurem)

Unethical experiments

The River Person's warning is the main source for this one though it is boosted by his stats being connected to 666, a number associated with evil. Parallels are drawn by the Gaster followers to W.D. and Alphys, who performed the DT experiments and hid the failures in an unethical manner, also provide support for this headcanon. What the experiments are exactly vary wildly with different canons.


A more recent hypothesis to appear is that the W.D. Gaster seen is some kind of amalgation and that he/they fell into the D.T extraction machine instead of the CORE. There isn't much evidence supporting this one other than visual similarities between the sprite and other amalgamates. This being said, the tarot card could support either fall theory as the bottom of the card looks similar to the core while the top looks like the extraction machine.

Magic hands

An ability commonly used in many AUs but one that seemingly has 0 support in the Undertale canon except him being referred to as the man that speaks in hands.

List of AUs involving W. D. Gaster

"Hello. He-he-he-he-have some respect and don't spoil the game. It's impossible to have mysteries nowadays, because of nosy people like you. Please keep all of this between us. If you post it online, I won't make any more secrets. No one will be impressed. It will be your faaaaault! He-he-he-he-ha-he-he-ha-he-he.

Abc 123 a
– [REDACTED] and Gaster's Followers

In Battle

See W. D. Gaster/In Battle.


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