Question: Which season did the Simpsons episode that Huell Howser appeared in air?

Context paragraphs:
Aaron Aaronsohn: Not to be confused with Aaron A. Aaronson, a fictional character in the Simpsons episode Sideshow Bob Roberts.

Rue des Lombards: The rue des Lombards is a street in Paris, France which is famous for hosting three of the main French jazz clubs : Le Baiser Salé, Le Duc des Lombards and the Sunset/Sunside.  It was originally a banking center in medieval Paris, a trade dominated by Lombard merchants.  It was also shown on the Simpsons episode "To Courier with Love".

Four Great Women and a Manicure: "Four Great Women and a Manicure" is the twentieth episode of the twentieth season of "The Simpsons".  First broadcast on the Fox network in the United States on May 10, 2009, it was the second Simpsons episode (after "Simpsons Bible Stories") to have four acts instead of the usual three.  The episode tells four tales of famous women featuring "Simpsons" characters in various roles: Selma as Queen Elizabeth I, Lisa as Snow White, Marge as Lady Macbeth and Maggie as Howard Roark from Ayn Rand's "The Fountainhead".

Patty and Selma: 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 Happy Wanderers: The Happy Wanderers was a nationally syndicated travelogue television show that originally aired on KTLA, Channel 5 in Los Angeles, California in the 1960s.  The weekly program featured travel destinations, tips, expenses, and highlights.  The series was originally produced by Barry Weinstein, David Eisenlohr and Charles Sutton, narrated by Stan Bohrman, which featured Slim Barnard and Henrietta Barnard.  Co-hosts included Milas Hinshaw and Buddy Noonan, who was executive producer.  The Happy Wanderer theme song by Friedrich W. Moller, with lyrics by Antonia Ridge, was scored by David Dunn Productions of Hollywood, CA.  Sponsored by local area Ford dealers, the show received an ARB and Nielsen rating of 15 as of June 2, 1965, making that series the most popular local television show in Southern California.  Television personality Huell Howser later featured Slim and Henrietta Barnard on his show, "Visiting with Huell Howser".

California's Gold: California's Gold is a public television human interest program that explores the natural, cultural, and historical features of California.  The series ran for 24 seasons beginning in 1991, and was produced and hosted by Huell Howser in collaboration with KCET, Los Angeles.  The series ceased production when Howser retired in November 2012, shortly before his death on January 7, 2013, although episodes continued to be shown for some time after his death.  In May 2016, KCET showed a "lost" episode on the Charles F. Lummis House, now considered to be the final episode.

O Brother, Where Bart Thou?: "O Brother, Where Bart Thou?"  is the eighth episode of "The Simpsons"' 21st season.  It originally aired on the Fox network in the United States on December 13, 2009.  In this episode, Bart goes on a quest to get a baby brother out of jealousy of the sisterly bond Lisa has with Maggie.

A Test Before Trying: "A Test Before Trying" is the tenth episode of the 24th season of "The Simpsons" and the 518th episode overall.  It first aired on the Fox network in the United States on January 13, 2013.  The episode is dedicated to the memory of Huell Howser, who appeared in the episode "O Brother, Where Bart Thou? ".  In the Season 16 episode, "There's Something About Marrying", the travel journalist (who has a similar name), that gave Springfield a score of 6/10, thereby causing the town to lose its tourists was based on him.  The character in that episode was voiced by Karl Wiedergott.

LA Urban Rangers: The Los Angeles Urban Rangers is a group of scholars and artists who interpret domestic and international urban landscapes using the perspective of the United States National Park Service.  The group develops "guided hikes, campfire talks, field kits, and other interpretive tools to spark creative explorations of everyday habitats."  Their most recent and longest-running outing - the Malibu Public Beach Safari - has been featured in media reports and by Huell Howser on his show.  The group was formed to highlight all the wonders of Los Angeles—both concrete and natural.

A Star Is Born Again: "A Star Is Born Again" is the 13th episode from "The Simpsons"<nowiki>'</nowiki> fourteenth season.  It first aired on the Fox network in the United States on March 2, 2003.  The episode owes much of its plot to "Notting Hill" (1999).  While that film is about an actress (Julia Roberts) finding happiness with the owner of an independent bookstore, the Simpsons episode features Hollywood movie star Sara Sloane (Marisa Tomei) falling for Ned Flanders after visiting the Leftorium.

Supporting paragraphs: A Test Before Trying O Brother, Where Bart Thou?
Answer: 21st