Unless you’re a dirty hacker, of course!
In order to achieve the ending, you have to access the files that Toby Fox used to create the game. These are not attainable via the local files downloaded with the executable game file. But, you have to find a way to access the code in the game itself.
If it’s difficult to see in the video, Youtuber Mir Rawrs is using XVI32, a hex editing program to access the game’s binary code by presenting it in a hexadecimal pattern. In the video, the creator swaps the code for the ending he is about to get with the impossible ending.
Theoretically, you can also get this ending by setting two contradictory values, like that you did and did not kill a certain character. However, you would have to find a way to do that without crashing the game.
- Mir Rawrs explains their process in the Youtube comments
Toby Fox seems to be the master at tying up loose ends. The fact that he anticipated hackers and addressed them directly make for a fun easter egg, to say the least.
