The couch gag for this episode is a parody of the Bayeux Tapestry. The Simpsons go to war with Flanders for the couch.
The title is based on the United States' motto found on the Great Seal, "E. pluribus unum", Latin for "Out of many, one."
Lisa states the most obvious implausibility of the story line, that Ralph is only eight years old and the Constitution requires the president to be at least 35, though several other aspects of the plot could not happen in real life. Springfield could not hold its own presidential primary as only states hold primaries, not individual cities. Also, for moving its primary date before New Hampshire, Springfield likely would have been penalized by being stripped of its delegates, and candidates would not campaign in the state, as was the case in 2008 when Michigan and Florida moved their primaries to January without the permission of the Democratic National Committee.
Oddly, Barack Obama is not mentioned in the episode at all, despite formally announcing his candidacy in February 2007, nearly a full year before this episode aired.