Gaster don’t be in game. Maybe he’s an easter egg, maybe not.

Alphys, Flowey — can be in game. I thought about this when I play Undertale (Omega Flowey):
All souls been by a rainbow colours. And they all started when Chara (determination) falled down. When she/he died, Asriel died too.

After all this there was another: Orange soul! Then: yellow, green, sky blue, blue and… Purple!

After all this I think, Flowey can be in game! Alphys, of course, too! Estelle, Gerson, Undyne would be in game! Without they this can’t be a game w

Generally: I create all this. Goodbye and until new news my friends!