Double-click flag so that the music syncs! You can replace characters by going into their costumes and replacing the poses with your characters' poses. You can also change some of the animation code if you want it to look different. I also made custom note skins
Story (This is apart of TOT (Main Timeline)'s Cannon): Shortly before Gaster's downfall his sons tried to convince him not to go through the experiment this is a montage of that situation and unfortunately for them it did not go well and despite the warnings Gaster went through the experiment anway
