Every time you start or "reset" Undertale, a specific number from 1-100 is selected as a "fun value". The value determines some things that can occur in the game like the Goner Kid or Phone number song.
The question is, what fun number value do you need for the door in waterfall to appear that leads to W.D Gaster?
1 Answer
From what I can discern, you want to know what the exact fun value is that you need so that Gaster, an NPC easter-egg character from Undertale will appear in your playthrough.
A quick glance on the Undertale Wiki reveals that the fun value you need is 66.
