Ah, yes. Readers have reminded me that And Maggie Makes Three is a prequel episode in which Homer does in fact briefly quit his job.
He quits by riding Mr Burns through the nuclear plant while playing his head like a bongo drum. This comes after clearing his debts and lining up a low-stress dream job, so he has a decent enough escape plan too. Hooray for Homer!
Alas, all does not go to plan. When he returns to Sector 7G, tail between his legs, he’s confronted by this: