I was trying to figure out how many you could stack, just going by the SRD. I think the best you can do is:
Ghost Half-Dragon Half-Field Petitioner Worm that Walks Demilich Lich Pseudonatural Vampire Celestial Lycanthrope Fiendish Phrenic Paragon Human
That has everything but Skeleton, Zombie, and Half-Celestial. Skeleton and Zombie make you mindless (which keeps you from becoming a Worm that Walks) and require a skeleton (which a Worm that Walks doesn’t have). Half-Celestial requires you be good or neutral, and turns you into an outsider, which only a Worm that Walks or Half-Dragon could undo. And it would work great with Half-Fiend if it wasn’t for each one forcing an alignment the other restricts. I don’t think any of the ones that don’t change creature type change alignment.


Here’s a way to have everyone meet based on this post: The first person makes up any backstory. The second person explains how they’re somehow involved in the first. Then maybe when you get to the end, the first guy goes again, and explains how his story is related to the last guy.