There's a shrewd link between the season two episode Oh Brother, Where Art Thou? and season four favourite Mr Plow which will have gone unnoticed by all but the most eagle-eyed viewers.
The company which manufactures Homer's plough might sound a tad familiar: Kumatsu Motors. This is the same business that purchased the motor firm Homer ruined during season two.
In Oh Brother, Where Art Thou? Homer bankrupts his half-brother Herb's Powell Motors by designing his "everyman car". At the end of the episode, the stricken firm was bought out by none other than Kumatsu Motors.
Had Homer not run Powell Motors into the ground, they might have designed the plough he famously purchased two seasons later.