S E C R E T S

What are you doing?

Looking for secrets?

Don't put your nose where it doesn't belong.

Or you might learn something you DON'T like...

If you continue down this path... you are going to have a bad time.

Maximum spoiler warning for the entire page. You have been warned.




THE GAMES ROOMS ARE BEING INDEXED HERE:
https://docs.google.com/document/d/1h_vdEFZMtefD-nkCZ7ODzArp7BRbGgN0_7HQ1XjTT8Y/edit
ASRIEL needs YOU to look for secrets! Do your part!

Sans:
On a conventional playthrough, it is entirely possible for the player to miss Sans' special abilities. Besides his extensive knowledge of Level Of ViolencE and EXecution Points, they seem largely normal.
On a genocide run, however, it will turn out that Sans is not only the one of the most powerful entity in the game (with the hardest fight), but also has the ability to time travel. Their dialogue strongly implies they have quite a bit of experience doing so.
By reloading the save before being judged by Sans, you will get his secret passwords. After three times, Sans will give you the key to his room. This needs to be done a pacifist run.
In Sans room a series of photos can be found (mentioned in text only) that hint at Sans time travel ability. Some people have had graphical "glitches" occure in the room, for others the game close by itself.
According to one dataminer, Sans room has a series of scripts dedicated to it that check for date, time, steps, etc. (Speculation until confirmed.)

The ferryperson:
Hints at numerous secrets. The most covert would be "Beware of the man who speaks in hands".


Save editing:
FUN 63 HAS BEEN SHOWN TO YIELD THE MOST RESULTS. NO GO AND EXPERIMENT MY BEAUTIES!!

Gaster:
A complete enigma. All we know is that they were the royal scientist before Alphys took over.
There is only one confirmed, direct reference to Gaster by an NPC who mentions the above, that they are 'holding a piece of him' and then the NPC disappears.
Some players have reported unique events and NPC dialogue related to doing a Gaster run (achieved by changing save0 and .ini files). Unconfirmed for now, as it might be tied to the 'Fun'/'fun' value instead.
Likewise, some players have mentioned the fun value decreasing faster than in other runs while playing under 'Gaster'.

Windings:
By editing the save0 and .ini file and setting the room to "264", a series of windings will appear. These translate to:
"ENTRY NUMBER SEVENTEEN

DARK

DARKER

YET DARKER

THE DARKNESS

KEEPS GRWOWING

THE SHADOWS

CUTTING DEEPER

PHOTON

READINGS

NEGATIVE

THIS NEXT

EXPERIMENT

SEEMS

VERY

VERY

INTERESTING

…

WHAT DO YOU

TWO THINK"
Via datamining it has been confirmed "Gasters_room" is in the game. See 'datamining' for more.

(Seemingly) isolated events:
Editing certain files, from changing the 'fun' variable to changing zeroes to ones, has yielded a number of results...
Universally characters become depressed.
Invisible pathways appearing.
Unreachable rooms becoming reachable. See below.
Unique events, such as the grey monsterkid pondering its own existence.
Neighbourly clampeople appearing.
Locked doors opening, such as Sans room and shed.

Hidden rooms:
The 'art room' being the best example, as it has a unique enemy within it which is well aware of its own mysteriousness.
A largely empty room with a single entity in the middle. Its face looks quite similair to Uboa from Yume Nikki.
A completely empty room wherein an entity fades in after being approached. It speaks in windigs. Translated to "[redcated]"
A soundtest room where several oggs can be played, see below.



Datamining:
Unused .ogg files:
mus_st_happytown.ogg, mus_st_him.ogg, mus_st_meatfactory.ogg, mus_st_troubledingle.ogg, have been found in the hidden, not normally accessible sound test room. must_st_his.ogg is explicitely refered to as "Gasters theme".
Maybe most notable in the entire folder is abc_123_a.ogg, which is a series of synthesized voices berating the player for datamining and mentioning Toby will never hide secrets in a game again. Smoking gun or false flag? Up to you.

 A "room0" has been found, filled with instruction on how to play the game. (It is possible this was made for testers and kickstarter backers.)
http://i.imgur.com/xttWrmE.png

A conversation was found, though the character talking is uncertain. What is, certian, however is that they are addressing the player. http://i.imgur.com/gj7W12g.png

Through datamining Flowey post-game dialgoue was uncovered. In one scenario Flowey directly references (what seems to be) Sans.

Gaster
Datamining revealed the follow dialogue/text relating to Gaster:
"It makes sense why ASGORE took so long to hire a new Royal Scientist. After all, the old one.. Dr. Gaster. What an act to follow! They say he created the CORE. However, his life… Was cut short… One day, he fell into his creation, and… Will Alphys end up the same way. L…I understand why ASGORE waited so long to hire a new Royal Scientist. The previous one, Dr. Gaster… His brilliance was irreplaceable. One day, his experiments went wrong, and…"
http://i.imgur.com/iV56hrX.png
This dialogue has been found in game by setting 'Fun' to 63. Spoken by grey NPCs.

Furthermore:
'Gaster's Theme
obj_gaster_follower_a
obj_gaster_follower_b
obj_gaster_follower_c
These objects were directly under the obj_gaster_follower items:
obj_greydoor
obj_mysteryman
obj_wrongnumbersong
obj_otherphonecall
obj_gaster_room
obj_gasterblaster
obj_gasterbl_gen
room_gaster'
Were found as well.