Question: "They Saved Lisa's Brain" is the twenty-second episode of "The Simpsons"' tenth season, when which recurring character from the animated television series "The Simpsons", and is voiced by Dan Castellaneta?

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Barney Gumble: Barnard "Barney" Gumble is a fictional character on the American animated sitcom "The Simpsons".  The character is voiced by Dan Castellaneta and first appeared in the series premiere episode "Simpsons Roasting on an Open Fire".  He is the town drunk of Springfield and Homer Simpson's best friend.  His desperation for alcohol is a frequent butt of jokes on the show.  Barney sobered up in the episode "Days of Wine and D'oh'ses", which was co-written by Castellaneta, and stayed sober for several seasons.  Barney was inspired by the cartoon character Barney Rubble from "The Flintstones" and by several barflies from other television programs.  In 2004, Castellaneta won an Emmy Award for voicing various characters, including Barney.

Mayor Quimby: Mayor Joseph Fitzgerald O'Malley Fitzpatrick O'Donnell The Edge Quimby, nicknamed Diamond Joe, is a recurring character from the animated television series "The Simpsons".  He is voiced by Dan Castellaneta, and first appeared in the episode "Bart Gets an F".  A member of the Democratic Party, Quimby is the mayor of Springfield, and is a composite parody of U.S. Senator Ted Kennedy and certain other members of the Kennedy family who have entered politics.

The Itchy &amp; Scratchy &amp; Poochie Show: "The Itchy & Scratchy & Poochie Show" is the fourteenth episode in the eighth season of the American animated television series "The Simpsons".  It originally aired on the Fox network in the United States on February 9, 1997.  In the episode, "The Itchy & Scratchy Show" attempts to regain viewers by introducing a new character named Poochie, whose voice is provided by Homer.  The episode is largely self-referential and satirizes the world of television production, fans of "The Simpsons", and the series itself.  It was written by David X. Cohen and directed by Steven Dean Moore.  Alex Rocco is a credited guest voice as Roger Meyers, Jr. for the third and final time (having previously provided the character's voice in "Itchy & Scratchy & Marge" and "The Day the Violence Died"); Phil Hartman also guest stars as Troy McClure.  Poochie would become a minor recurring character and Comic Book Guy's catchphrase, "Worst episode ever", is introduced in this episode.  With "The Itchy & Scratchy & Poochie Show", the show's 167th episode, "The Simpsons" surpassed "The Flintstones" in the number of episodes produced for a prime-time animated series.

Clown in the Dumps: "Clown in the Dumps" is the season premiere of the twenty-sixth season of the American animated television series "The Simpsons", and the 553rd episode of the series overall.  It first aired in the United States on the Fox network on September 28, 2014, with "The Simpsons Guy", a crossover episode of "Family Guy" with "The Simpsons", airing afterwards.  This episode was dedicated in memory of Louis Castellaneta, the father of "The Simpsons" voice actor Dan Castellaneta.  It was written by Joel H. Cohen and directed by Steven Dean Moore, with Don Hertzfeldt directing a sequence in the opening titles.  Jeff Ross, Sarah Silverman and David Hyde Pierce guest starred as themselves, with Jackie Mason and Kelsey Grammer reprising their respective roles as Rabbi Krustofski and Sideshow Bob, while Maurice LaMarche voiced several minor characters.

Hans Moleman: Hans Moleman is a recurring character on the animated television series "The Simpsons".  He was created by series creator Matt Groening and is voiced by Dan Castellaneta and first appeared in the episode "Principal Charming".  His appearance usually comes in the form of a running gag, in which, as a bystander to disastrous events, he suffers unfortunate, often seemingly fatal accidents, only to return in later episodes completely unharmed.

Krusty the Clown: Herschel Shmoikel Pinchas Yerucham Krustofsky, better known as Krusty the Clown (sometimes spelled as Krusty the Klown), is a cartoon character in the animated television series "The Simpsons".  He is voiced by Dan Castellaneta.  He is the long-time clown host of Bart and Lisa's favorite TV show, a combination of kiddie variety television hijinks and cartoons including "The Itchy & Scratchy Show".  Krusty is often portrayed as a cynical, burnt-out, addiction-riddled smoker who is made miserable by show business but continues on anyway.  He has become one of the most common characters outside of the main Simpson family and has been the focus of several episodes, most of which also spotlight Bart.

Grampa Simpson: Abraham Jedediah Simpson II, often known as Grampa, is a fictional character in the animated television series "The Simpsons".  He made his first appearance in the episode entitled "Grampa and the Kids", a Simpsons short on "The Tracey Ullman Show".  Voiced by Dan Castellaneta, he is the father of Homer Simpson and the grandfather of Bart, Lisa and Maggie Simpson.  In the 1000th issue of "Entertainment Weekly", Grampa was selected as the Grandpa for "The Perfect TV Family".

Groundskeeper Willie: Dr. William MacDougal, usually known as Groundskeeper Willie, is a recurring character on "The Simpsons", voiced by Dan Castellaneta.  He is the head groundskeeper at Springfield Elementary School.  Willie is almost feral in nature and is immensely proud of his native Scotland.  He is easily identifiable by his flaming red hair and beard, as well as his aggressive temperament and thick though inaccurate Scottish accent.

They Saved Lisa's Brain: "They Saved Lisa's Brain" is the twenty-second episode of "The Simpsons"' tenth season.  It first aired on the Fox network in the United States on May 9, 1999.  In the episode, after writing a thoughtful letter to the "Springfield Shopper", Lisa is invited to join the Springfield chapter of Mensa.  When Mayor Quimby later flees Springfield, the group takes control of the town, hoping to improve the lives of Springfieldians through the rule of the smartest.  Meanwhile, Homer poses for a series of erotic photos.

The Itchy &amp; Scratchy Show: The Itchy & Scratchy Show (often shortened as Itchy & Scratchy) is a running gag and fictional animated television series featured in the American animated television series "The Simpsons".  It usually appears as a part of "The Krusty the Clown Show", watched regularly by Bart Simpson and Lisa Simpson.  Itself an animated cartoon, "The Itchy & Scratchy Show" depicts a sadistic anthropomorphic blue mouse, Itchy (voiced by Dan Castellaneta), who repeatedly maims and kills an anthropomorphic, hapless threadbare black cat, Scratchy (voiced by Harry Shearer).  The cartoon first appeared in "The Tracey Ullman Show" short "The Bart Simpson Show", which originally aired November 20, 1988.  The cartoon's first appearance in "The Simpsons" was in the 1990 episode "There's No Disgrace Like Home".  Typically presented as 15-to-60-second-long cartoons, the show is filled with gratuitous violence.  "The Simpsons" also occasionally features characters who are involved with the production of "The Itchy & Scratchy Show", including Roger Meyers Jr. (voiced by Alex Rocco, and, later, Hank Azaria), who runs the studio and produces the show.

Supporting paragraphs: They Saved Lisa's Brain Mayor Quimby
Answer: Mayor Quimby