Developers' Room
In Snowdin, there is a large door that normally doesn't open for you, To open it, complete the credits without touching a single name, and beyond you'll find the developers' room.
Hard Mode
To activate hard mode, enter "Frisk" as your starting name. You'll get a warning that this will "make your life hell"; confirm to begin playing hard mode. The changes include not being able to flee on the first turn of battles, toughened and new enemies, and only being able to hold three pieces of candy, among other things.
