Board Thread:Questions and Answers/@comment-29905311-20170130083321/@comment-27701762-20170131103515

By the way, here's a fun fact:

The second little speech once you reach the midpoint of the battle (the "friendship, it's great" one) is tied to a variable in the "undertale.ini" file called "SS." The variable is not present at all originally, and is created and set to 1 when you accept Sans's offer of mercy.

That in itself isn't all that interesting, but two things stem from that fact:

1) The only other permanent change in the game files that is known within all of Undertale is the consequence of finishing a Genocide run. And while there is a change in the files, that change does not occur in the "undertale.ini" file (which is wiped whenever you perform a True Reset, whether by completing a TP or Gen run), or in any of the "file#" files associated with a particular playthrough, but in a couple of "system_information" files.

2) Since all the game is looking for is the "SS" variable set to something it can read, you can just paste SS="1.000000" under the [Sans] heading within the "undertale.ini" file. And guess what? The game will give you the "friendship, it's great" speech instead of the longer speech. This could be done even if, say, you haven't even reached Sans, making it look like you're fighting him for the very first time and he's giving the shortened speech on a fresh run.