Lisa Simpson in the context of "Mona Simpson (The Simpsons)"

"D'oh!" (/doʊʔ/ ) is the most famous catchphrase used by the fictional character Homer Simpson, from The Simpsons, an animated sitcom. It is an exclamation typically used after Homer injures himself, realizes that he has done something foolish, or when something bad has happened or is about to happen to him. All his prominent blood relations—son Bart, daughters Lisa and Maggie, his father, his mother and half-brother—have also been heard to use it themselves in similar circumstances. On a few occasions, Homer's wife Marge and characters outside the family such as Mr. Burns and Sideshow Bob have also used this phrase.

In 2006, "d'oh!" was listed as number six on TV Land's list of the 100 greatest television catchphrases. The spoken word "d'oh" is claimed as a sound trademark by the owner of The Simpsons, 20th Century Studios. Since 2001, the word "doh" has appeared in the Oxford English Dictionary, without the apostrophe. Early recorded usages of the sound "d'oh" are in numerous episodes of the BBC Radio series It's That Man Again between 1945 and 1949, but the OxfordWords blog notes "Homer was responsible for popularizing it as an exclamation of frustration." The term also appeared in an early issue of Mad comics, with a different spelling but the same meaning, in issue 8 (December 1953 – January 1954); in a one-page story by Harvey Kurtzman entitled "Hey Look!", a man seeking peace and quiet suddenly hears a loud radio and, grimacing, says, "D-oooh – the neighbors [sic] radio!!"

Homer Jay Simpson is the main protagonist of the American animated sitcom The Simpsons. Part of the titular family, Homer made his television debut in the short "Good Night" on The Tracey Ullman Show on April 19, 1987. Cartoonist Matt Groening crafted and designed Homer while waiting in the lobby of James L. Brooks's office. Initially called to pitch a series of shorts based on his comic strip Life in Hell, Groening instead developed a new set of characters. After two years on The Tracey Ullman Show, the Simpson family received their own series, which premiered on Fox on December 17, 1989.

Homer is the patriarch of the family; he is married to Marge, with whom he has three children, Bart, Lisa, and Maggie. As the family's primary provider, Homer primarily works as a safety inspector at the Springfield Nuclear Power Plant. He represents numerous American working-class stereotypes: he is overweight, balding, immature, unintelligent, outspoken, aggressive, lazy, ignorant, unprofessional, and deeply fond of beer, junk food, and television. Despite these flaws, Homer is fundamentally a kind-hearted man and fiercely protective of his family, particularly during crucial moments.

The Simpsons is an American animated sitcom created by Matt Groening and developed by Groening, James L. Brooks and Sam Simon for the Fox Broadcasting Company. It is a satirical depiction of American life, epitomized by the Simpson family, which consists of Homer, Marge, Bart, Lisa, and Maggie. Set in the fictional town of Springfield, in an unspecified location in the United States, it caricatures society, Western culture, television and the human condition.

The family was conceived by Groening shortly before a solicitation for a series of animated shorts with producer Brooks. He created a dysfunctional family and named the characters after his own family members, substituting Bart for his own name; he thought Simpson was a funny name in that it sounded similar to "simpleton". The shorts became a part of The Tracey Ullman Show on April 19, 1987. After three seasons, the sketch was developed into a half-hour primetime show and became Fox's first series to land in the Top 30 ratings in a season (1989–1990).

Margaret Lenny "Maggie" Simpsonis a character in the animated television series The Simpsons and the youngest member of the Simpson family. She first appeared on television in the Tracey Ullman Show short "Good Night" on April 19, 1987. Maggie was created and designed by cartoonist Matt Groening while he was waiting in the lobby of James L. Brooks' office. She is also known as the “baby” of the Simpson family. She received her first name from Groening's youngest sister. After appearing on The Tracey Ullman Show for three years, the Simpson family was given their own series on the Fox Broadcasting Company, which debuted on December 17, 1989.

Maggie is the youngest child of Homer and Marge, and the younger sister to Bart and Lisa. She is often seen sucking on her red pacifier and, when she walks, she trips over her clothing and falls on her face (this running gag is used much more in earlier seasons). Being an infant, she has not yet learned how to talk. However, she did appear to talk in the first Tracey Ullman Show short.

Abraham Jay "Abe" Simpson II, better known as Grampa Simpson, is a recurring character in the animated television series The Simpsons. He made his first appearance in the episode entitled "Grandpa and the Kids", a one-minute Simpsons short on The Tracey Ullman Show, before the debut of the television show in 1989.

Grampa Simpson is voiced by Dan Castellaneta, who also voices his son, Homer Simpson. He is the paternal grandfather of Bart, Lisa and Maggie Simpson. In the 1,000th issue of Entertainment Weekly, Grampa was selected as the "Grandpa for The Perfect TV Family". Grampa is a World War II veteran and retired farmer who was later sent to the Springfield Retirement Castle by Homer. He is known for his long, rambling, often incoherent and irrelevant stories and senility.

The Simpson family are the titular main characters featured in the animated television series The Simpsons. The Simpsons are a nuclear family consisting of married couple Homer and Marge and their three children, Bart, Lisa, and Maggie. They live at 742 Evergreen Terrace in the fictional town of Springfield, United States. They were created by cartoonist Matt Groening, who conceived the characters after his own family members, substituting "Bart" for his own name. The family debuted on Fox on April 19, 1987, in The Tracey Ullman Show short "Good Night" and were later spun off into their own series, which debuted on Fox in the United States on December 17, 1989, and started airing in Winter 1990.

Alongside the five main family members are Homer's father Abraham "Grampa" Simpson, Marge's sisters Patty and Selma Bouvier, and the family's two pets, Santa's Little Helper and Snowball II; all of them feature in major supporting roles. Other, less prominent relatives that appear infrequently include Marge's mother Jacqueline Bouvier, Homer's mother Mona Simpson, his half-brother Herb Powell and minor relatives.

Marjorie Bouvier "Marge" Simpson (née Bouvier) is one of the main characters in the American animated sitcom The Simpsons and part of the eponymous family. Voiced by Julie Kavner, she first appeared on television in The Tracey Ullman Show short "Good Night" on April 19, 1987. Marge was created and designed by cartoonist Matt Groening while he was waiting in the lobby of James L. Brooks' office. Groening had been called to pitch a series of shorts based on Life in Hell but instead decided to create a new set of characters. He based the character on his mother Margaret Groening. After appearing on The Tracey Ullman Show for three seasons, the Simpson family received their own series on Fox, which debuted December 17, 1989.

Marge is the matriarch and housewife of the Simpson family. With her husband Homer, she has three children: Bart, Lisa, and Maggie. Marge is the moralistic force in her family and often provides a grounding voice in the midst of her family's antics by trying to maintain order in the Simpson household. She cooks, cleans, and without her in the Simpson family, they would be in despair. She is often portrayed as a stereotypical television mother and is often included on lists of top "TV moms". She has appeared in other media relating to The Simpsons—including video games, The Simpsons Movie, The Simpsons Ride, commercials, and comic books—and inspired an entire line of merchandise.

Robert Underdunk "Bob" Terwilliger Jr., PhD, better known as Sideshow Bob, is a recurring character and the secondary antagonist in the animated television series The Simpsons. He is voiced by Kelsey Grammer and first appeared in the episode "The Telltale Head". Bob is a self-proclaimed genius who is a graduate of Yale University and a champion of high culture, including the adoption of a transatlantic accent, similar to that of Grammer's portrayal of Dr. Frasier Crane from the sitcoms Cheers and Frasier. He began his career as a sidekick on Krusty the Clown's television show, but after enduring constant abuse, Bob framed his employer for armed robbery in "Krusty Gets Busted", only to be foiled by Bart Simpson, and sent to prison. Bob started seeking revenge against Bart while in prison, and the two became feuding archenemies.

Bob made his second major appearance in season three's "Black Widower"; the writers echoed the premise of Wile E. Coyote chasing the Road Runner by having Bob unexpectedly insert himself into Bart's life, threatening to disrupt and end it through murder. Starting with that appearance and thereafter, Bob has assumed the role on The Simpsons of an evil genius. Episodes in which he is a central character typically involve Sideshow Bob being released from prison and executing an elaborate revenge plan, usually foiled by Bart and Lisa. His plans often involve death and destruction, usually targeted at Bart or, less often, Krusty, though he starts targeting the entire Simpson family in season 17. In season 27, however, during the first segment of "Treehouse of Horror XXVI", entitled "Wanted: Dead, Then Alive", Bob finally gets his wish of killing Bart, commenting that he spent 24 years trying to kill a ten-year-old child; however, he becomes bored with Bart dead, so he brings him back to life so that he can repeatedly kill Bart over and over again.