Intro Story Glitch | Creepy Castle Early (Post-Playthrough) @IntroStoryGlitch | Uploaded July 2014 | Updated October 2024, 2 hours ago.
The file I enter at the beginning allows me to set up the flashback spot (Cranky in Castle), which I warp to in another file. See 2:06.

Before you start the trick, the setup file must have keys 3 and 8 as well as all moves required to beat K. Rool.

1. Activate Intro Story Glitch
2. Enter your setup file
3. Enter Castle within 55 seconds and go to Cranky, Funky, Snide or Troff 'n' Scoff
4. Trigger an Intro Story fadeout (T&S: instrument or tag barrel)
5. Beat K. Rool
6. Start the file in which you want to enter Castle early
7. Enter and exit Cranky's lab

As of now, it is still impossible to enter Castle early without a setup file.