Due to the show's floating timeline, his age remains the same over the years, and newer episodes still depict him as a World War II veteran.

Grampa is a veteran of World War II, where he served as Master Sergeant of the Flying Hellfish unit which included himself (the Unit Commander, Radio Operator Sheldon Skinner (Seymour Skinner's father), Private Fifth Class Arnie Gumble (Barney Gumble's father), Asa Phelps, Iggy Wiggum (Clancy Wiggum's father), Milton "Oxford" Haas, Etch Westgrin, Griff McDonald, Private Charles Montgomery Burns and Grey Fox.

[12] At the very end of the war in Europe, Grampa's unit "liberated" a stash of priceless art from surrendering German forces.

She became a fugitive from justice after she abetted in the sabotage of a biological weapons research lab owned by Mr. Burns to deliberately poison everyone in Springfield.

[15] It is recurringly suggested that, while caring, Grampa was a strict disciplinarian who could be very controlling, neglectful, and even emotionally abusive towards Homer when he was growing up and he still had not forgiven him for that.

In the season four episode, "The Front", Grampa tells Roger Myers Jr., head of Itchy and Scratchy studios, that he worked as a cranberry silo night watchman for forty years.

A running gag in the show usually has Grampa in a cameo episode appearance where he wonders where everyone is or wishes to be noticed by the family.

[19] Matt Groening, creator of The Simpsons, wanted to have a character that was "really cranky" and old, and who complained a lot and invented stories to tell to children, so he created Grampa.

[20] Bill Oakley and Josh Weinstein, former writers on the show, said that they liked to write episodes about Grampa because they are "obsessed" with old people.

Castellaneta was part of the regular cast of The Tracey Ullman Show and had previously done some voice-over work in Chicago alongside his wife Deb Lacusta.

[27] Castellaneta likes to stay in character during recording sessions,[28] and tries to visualize a scene in his mind so that he can give the proper voice to it.

Sexual Inadequacy" (season six, 1994) featured many interactions between Grampa and Homer, so Castellaneta therefore had to talk to himself when he recorded the voices for that episode.

[3] Joe Rhodes of TV Guide considered Grampa's most memorable line to be "If I'm not back at the home by nine, they declare me legally dead and collect my insurance.

"[20] Dan Castellaneta has won two Primetime Emmy Awards in the Outstanding Voice-Over Performance category for voicing various characters, including Grampa.

"[36] DVD Movie Guide's Colin Jacobson said in a review of the same episode that Grampa is "always fun" and "it’s nice to see him in an ebullient mood, at least for a while.

"He yelled, used corporal punishment, and constantly belittled Homer's attempts to have fun, date, and excel at various activities," they added.

[40] In his book Understanding the Psychology of Diversity, author Bruce Evan Blaine wrote that Grampa is typically portrayed as a "doddering", "senile", and "dependent" person who is a "trivial" and "often disposable figure" in his son's life.

[43] Alongside the television series, Grampa regularly appears in issues of Simpsons Comics, which were first published on November 29, 1993.