Kinda Big Darkness Saga
The Kinda Big Darkness Saga was a ridiculous Classic LNH story, written by Dave Van Domelen and wrapped around the creation of the Looniverse MUSH. It featured Flipseid (or so it seems), his Savants of Darkness, and They Might Be Villains attacking the LNH and making a lot of TinyTIM references.
It established two surprisingly notable characters who didn't actually appear in the story itself, Flipseid and Dev-Null. An alternate version of this storyline told in Stranger Tales (where Flipseid did appear, much the worse for Loonivearth) served as Fearless Leader's origin.