A removed Gaster Encounter, brought back to life. Yes, this was supposed to be a real thing that would happen in the game. The code for it is in the game files, although it never was applied to the game. It was originally supposed to occur in Napstablooks farm, judging by the code, but I thought it would be cool if it would be like the Gaster door secret, with the extra hallway. So imagine you are in Blooky's farm when you see an extra hallway. You walk into it and this happens.
Stable Sprite - https://www.deviantart.com/toreodere/art/The-spooky-stable-ghost-Undertale-574045068 Original code for secret applied into game - https://www.youtube.com/watch?v=KU41xeEqIhk Weird creature - Spr_redacted_a_0 Text engine - Jerry_Jingle (tinkered with a bit)