How many story arcs reference a past arc?

Like for example the dirge of chaos story arc had a freakshow boss Killdozer appeared in the second villain clone arc "Good Villains Never Die", and the Dirge it's self was in the new chapter of "Who will die?"

Another example I noticed is that Jekins from the old villain tutorial shows/showed up in a couple of arcs (I'm not sure if these arcs were changed).

I've noticed Nebel Ubermenschen Force appears in a few arcs. And with a name like that it can't be a coincidence.

My favorite example of this is Pyriss, who you turn to the dark side in Peter Themari's arc in Port Oakes. She shows up later in one of Vernon von Grun's arcs and it is not a happy ending for her.