If you want to figure this out by yourself do not scroll down. Instructions: In the sprite that is a black box there will be a little box that says hack here ---> follow that and change it to a time that is better to get the secret ending. If you somehow don't know in the boss fight click on him to beat him.
Thanks to a high schooler that I don't know the name of for giving the suggestion of using a doom boss. Thanks to the undertale music project that's where I got the music: https://scratch.mit.edu/projects/89051979/ Also I really like this game and think it will be popular so I'm trying to get it on every studio I can. So if I'm following you or you're following me don't be surprised if this pops up on a bunch of your studios.