Dr. Nicholas Riviera (usually referred to as simply Dr. Nick) is a recurring fictional character in the American animated sitcom "The Simpsons".
 He is voiced by Hank Azaria and first appeared in the episode "Bart Gets Hit by a Car".
 Dr. Nick is an inept quack physician, and a satire of incompetent medical professionals.
 Upon entering a scene, Dr. Nick's catchphrase is "Hi, everybody!"
, with the characters present immediately responding (often in chorus) "Hi, Dr. Nick!"
.
Waylon J. Smithers Jr., usually referred to as Mr. Smithers or simply Smithers, is a recurring fictional character in the American animated sitcom "The Simpsons", who is voiced by Harry Shearer.
 Smithers first appeared in the episode "Homer's Odyssey", although his voice could be heard in the series premiere "Simpsons Roasting on an Open Fire".
 He is the consummate executive and personal assistant of Springfield Nuclear Power Plant's owner Mr. Burns.
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.
Troy McClure is a fictional character from the American animated sitcom "The Simpsons".
 He was voiced by Phil Hartman and first appeared in the second season episode "Homer vs. Lisa and the 8th Commandment".
 McClure is usually shown doing low-level work, such as hosting infomercials and educational films.
 He appears as the main character in "A Fish Called Selma", in which he marries Selma Bouvier to aid his failing career and quash rumors about his personal life.
 McClure also 'hosts' "The Simpsons 138th Episode Spectacular" and "The Simpsons Spin-Off Showcase".
Patty and Selma Bouvier ( ) are fictional characters in the American animated sitcom "The Simpsons".
 They are identical twins (but with different hairstyles) and are both voiced by Julie Kavner.
 They are Marge Simpson's older twin sisters, who both work at the Springfield Department of Motor Vehicles, and possess a strong dislike for their brother-in-law, Homer Simpson.
 Selma is the elder by two minutes, and longs for male companionship while her sister, Patty, is a lesbian.
 Kavner voices them as characters who "suck the life out of everything".
 Patty and Selma first appeared on the first ever aired Simpsons episode "Simpsons Roasting On An Open Fire", which aired on December 17, 1989.
"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.
"This Little Wiggy" is the eighteenth episode of "The Simpsons"<nowiki>'</nowiki> ninth season.
 It originally aired on the Fox network in the United States on March 22, 1998.
 It was written by Dan Greaney and directed by Neil Affleck.
 The episode sees Ralph Wiggum becoming friends with Bart.
 Phil Hartman guest stars as recurring character Troy McClure.
"Lisa Goes Gaga" is the twenty-second and final episode of the twenty-third season of the American animated sitcom "The Simpsons".
 It originally aired on the Fox network in the United States on May 20, 2012.
 In the episode, American singer-songwriter Lady Gaga makes a visit to Springfield, where all of its residents are in a state of depression.
 Main character Lisa Simpson is arguably the most depressed person in the city, prompting Gaga to go out of her way to teach Lisa the meaning of happiness.
"Lisa's Wedding" is the 19th episode of "The Simpsons"<nowiki>'</nowiki> sixth season.
 It originally aired on the Fox network in the United States on March 19, 1995.
 The plot focuses on Lisa visiting a carnival fortune teller and learning about her future love.
 It was written by Greg Daniels and directed by Jim Reardon.
 Mandy Patinkin guest stars as Hugh Parkfield and Phil Hartman guest stars as Troy McClure.
 The episode won an Emmy Award in 1995 for Outstanding Animated Program, becoming the third episode of "The Simpsons" to win the award.
"A Fish Called Selma" is the nineteenth episode of "The Simpsons"<nowiki>'</nowiki> seventh season.
 It originally aired on the Fox network in the United States on March 24, 1996.
 The episode features Troy McClure, who attempts to resurrect his acting career by marrying Selma Bouvier.
 Show runners Bill Oakley and Josh Weinstein were fans of Phil Hartman and wished to produce an episode that focused on his character McClure.
 Freelance writer Jack Barth wrote the episode, and Mark Kirkland directed it.

Question: Troy McClure is a fictional character from the American animated sitcom "The Simpsons" who appeared as the main character in an episode that aired when?
Answer: March 24, 1996