Board Thread:Wiki Discussion/@comment-31960778-20170721040405/@comment-32182236-20170903204049

Well, every time you enter in someone else's name for Chara (except for Frisk), said character will have a reaponse to that. We don't know why this is. However, the same thing would happen with Gaster. However, Gaster does not exist anymore, and merely watches over the timeline. So the game's calling for someone who doesn't exist to respond.. Someone who can't interact with the world around him.

That's an invalid action, causing the game to crash.

One could also argue that Gaster himself crashes the game. After all, they seem to have a say in what happens at times, such as Papyrus saying "I'LL ALLOW IT" if you type in "Papyru". I have a hypothesis about Hard Mode, that if true, would indirectly support this proposition, but I won't be getting much into it-It's quite a lengthy and strange one.