Did some digging a while ago, created a list of characters that I found in different base models and then forgot about it.
This is a wildcard list of characters that are natively included in either Pony, SDXL or Illustrious models.

Can neither confirm nor deny if they actually work perfectly on all three. But I've been using that wildcard recently and never saw any issues.

This list (or an even better one) is probably available somewhere else already, I just couldn't find it.

If you do have characters that are supposed to work but don't, please let me know. I will adjust the file.