Didn't realize there was a second hotfix. Will have to look into that.
Added in 28 minutes 21 seconds:
Figured it out. This seems like some sort of bizarre loading glitch.
I tried to recreate the glitch in the SMBX editor first. Didn't work.
I also tried recreating the glitch by loading up the Invasion 2 and playing the "Playful Playland" level. I tried playing it both in editor, and in game-actual. Glitch didn't happen.
But then I remembered that just prior to playing "The Invasion 2", I was playing "The New Great Castle Adventure"
So I loaded that save file up, played some of the level "Candy Craze Cliffs", and then exited the game mid-level.
It took me back to the vanilla "1.3 Style" loading screen, and from there I loaded "The Invasion 2"
Went back to level 18, or "Playful Playland", and the glitch happened.
Welp... This glitch is stupid.