Kinda new at making threads, so I hope this is okay in terms of asking for help.
I've pretty much completed the game, or so it seems, except I'm apparently missing 3 items out of the whole set. I've completed all 12 worlds and their golden chests, 11 dungeons and the sub-dungeons, Mooshtopia, World -1, that gold gem in World 6, and Professor Sans... but I'm only at 333/336 somehow:
I don't get it, what could I have missed? Do I have to catch 1 of each enemy or something?