I’ve been poking around that corner of the 'Grim Adventures' fandom for a while, and its staying power surprises me sometimes. It’s not the biggest ship out there, but the threads for it keep popping up year after year.
A huge part of it is the gap between what we saw and what we imagined. The show gave us this explosive, chaotic rivalry—Thrax, this literal embodiment of disease, versus Billy’s germ-obsessed dad. But it was all played for laughs, a one-off monster-of-the-week. Fanfiction takes that raw material and asks, 'What if it wasn’t?' What if that antagonism had weight, history, or even a strange mutual understanding? Writers get to build an entire dynamic from almost scratch, which is a powerful creative draw.
The dynamic itself is classic enemies-to-something-else. You’ve got order versus chaos, human obsession versus supernatural entity, a neat freak versus a walking biohazard. It’s inherently dramatic and ripe for tension. But the popular fics often subvert the obvious. It’s less about epic battles and more about the quiet, weird moments—Thrax manifesting in the Mandy-verse to complain about modern antibiotics, or Ozzy’s fixation taking a metaphysical turn. The appeal is in taking two joke characters and uncovering a strange, compelling gravity between them that the original never intended.