When Homer refers to Oregon as "the birthplace of Matt Groening," he mispronounces the show creator's last name as "Gro-ning"; Matt's last name is, according to The Simpsons 138th Episode Spectacular, pronounced "Gray-ning."
This episode disproves the common fan theory that Springfield is in Oregon because Homer must drive to Oregon from Springfield's location.
Further, the rings circling Fun Homer are a parody of the energy cage rings that encircled General Zod and his two minions during their sentencing at the beginning of Superman II.
On the Simpsons' website; it stated that this episode aired on the same date but originally in 2005. This has since been corrected.
Skinner's car is seen as a pre-owned Toyota Camry, which Skinner quotes that 1995 was a fine year for Camrys, even though his car spent three months in a lake which he says while admiring it in the school parking lot. It's never seen again after this episode, according to the episode guide it says that the steam leak destroyed it with the school.
In the German dub, this was the last episode in which Elisabeth Volkmann provided the voice of Marge Simpson. After Volkmann's sudden death in 2006, Anke Engelke took over. The German version of We're on the Road to D'oh-where is dedicated to Volkmann.
Lisa wouldn't be able to find a job to support herself and Maggie because of her age and child labor laws. Most Springfielders are either really stupid or really greedy. And who's to say that Lisa can't lie about her age in order to find work? Besides, Bart got jobs in episodes such as "Lisa the Tree Hugger" and "Bart the Murderer", as well as Nelson later owning a bike shop in which he employed people later on in "Loan-a Lisa".
In one scene, Wendell was sitting in his classroom. Two scenes later, he was practicing with the school band in another classroom.
We're on the Road to D'ohwhere is a take on the Talking Heads song “Road to Nowhere”. It may also refer to the famous series of Bob Hope/Bing CrosbyRoad to... movies, which have been spoofed multiple times by Family Guy. This is at least the third time that the Talking Heads have been referenced by the Simpsons, not including "Dude, Where's My Ranch?"
Intellectual Homer, who has been killed by Serious Homer, has written on the floor in his own blood "Ontogeny recapitulates phylogeny". This is the famous statement of Ernst Haeckel's recapitulation theory about the similarity of the embryonic development of organisms to its evolutionary history. Ironically, it has been debunked as a scientific principle. Presumably, Intellectual Homer wrote this before it was debunked, a testament to how long he had been dead.