Board Thread:General Discussion v2.0/@comment-24597765-20151127205619/@comment-25169188-20151221011420

This is what I think really sets undertale apart, the fact that it did something that big gaming companies have been trying to do for a long time, with little to no success, implement choice into the gameplay. And not just choice, but choice that changes the story dramatically. This gives undertale a beautiful replay value, there are multiple endings that all share a little bit (or a butt ton) of story information into the story, and there are so many things you will miss the first time or do differently the second time. Admittedly, an ending where you stayed with Goat Mom ... Uh... I mean Toriel... Would add further to this choice, but like mentioned above, it would really ruin the story. Very little happens in the ruins when compared to how much happens outside the ruins. Most of the story could never happen if you left the ruins.

All in all, if they did allow the option to stay with Toriel/Goat Mom, an event would have to happen that sent the player out of TorielGoatMom's home. Idunno, like, she had trouble taking care of you... Asgore came looking for you, and the ruins was his first stop... You get it.

And for the miniature ending with staying with her? Time would lapse and Frisk would have grown up a bit, enough for a noticeable change in appearance on his/her (i prefer her) sprite, and a new human would fall down, leave the ruins, and set free the underground, where you escaped with GoatTorielMom and lived together.