Question: What duo in the Simpsons episode "Gump Roast" usually appear in the Treehouse of Horror episodes? 
Context: "Treehouse of Horror XIII" is the first episode of "The Simpsons"<nowiki>'</nowiki> fourteenth season and the thirteenth Halloween episode.  It first aired on the Fox network in the United States on November 3, 2002, three days after Halloween.  It is the second Treehouse of Horror to have a zombie related segment, and the last Treehouse of Horror to have three separate writers credited for writing three stories (starting with "Treehouse of Horror XIV", only one writer is credited for writing the three stories). Treehouse of Horror, also known as "The Simpsons" Halloween specials, is a series of Halloween specials within the animated series "The Simpsons", each consisting of three separate, self-contained segments.  These segments usually involve the Simpson family in some horror, science fiction, or supernatural setting.  They take place outside the show's normal continuity and completely abandon any pretense of being realistic, being known for their far more violent and much darker nature than an average "Simpsons" episode.  The first, entitled "Treehouse of Horror", aired on October 25, 1990, as part of the second season and was inspired by EC Comics horror tales.  Since then, there have been 26 other "Treehouse of Horror" episodes, with one airing every year. Pleural plaques are indicators of asbestos exposure, and the most common asbestos-induced lesion.  They usually appear after 20 years or more of exposure and never degenerate into mesothelioma.  They appear as fibrous plaques on the parietal pleura, usually on both sides, and at the posterior and inferior part of the chest wall as well as the diaphragm. "Treehouse of Horror XXI" is the fourth episode of "The Simpsons"<nowiki>'</nowiki> twenty-second season.  It first aired on the Fox network in the United States on November 7, 2010.  This is the 21st "Treehouse of Horror" episode, and, like the other "Treehouse of Horror" episodes, consisted of three self-contained segments: In "War and Pieces", Bart and Milhouse discover a real-life board game that they must win to return home; in "Master and Cadaver", Marge and Homer go on a honeymoon on a sailboat, and rescue a mysterious castaway named Roger; and in "Tweenlight", Lisa falls in love with a vampire named Edmund. Kang and Kodos are a duo of fictional recurring characters in the animated television series "The Simpsons".  Kang is voiced by Harry Shearer and Kodos by Dan Castellaneta.  They are aliens from the fictional planet Rigel VII and appear almost exclusively in the "Treehouse of Horror" episodes.  The duo has appeared in at least one segment of all twenty-seven Treehouse of Horror episodes.  Sometimes their appearance is the focus of a plot, other times a brief cameo.  Kang and Kodos are often bent on the conquest of Earth and are usually seen working on sinister plans to invade and subjugate humanity. "Treehouse of Horror XIX" is the fourth episode of the twentieth season of "The Simpsons".  It first aired on the Fox network in the United States on November 2, 2008.  This is the nineteenth "Treehouse of Horror" episode, and, like the other "Treehouse of Horror" episodes, contains three self-contained segments: in "Untitled Robot Parody", Transformer robots run amok in Springfield; in "How to Get Ahead in Dead-Vertising", Homer is hired by ad agents to kill celebrities so their images can be used for free; and in a "Simpsons"-style parody of "It's the Great Pumpkin, Charlie Brown" (called "It's The Grand Pumpkin, Milhouse"), Milhouse summons a demon pumpkin who goes berserk when it sees humans carving its brethren into jack-o-lanterns as part of Halloween tradition.  It was written by Matt Warburton and directed by Bob Anderson. "Treehouse of Horror" is the third episode of "The Simpsons"<nowiki>'</nowiki> second season.  It originally aired on the Fox network in the United States on October 25, 1990.  The episode was inspired by 1950s horror comics, and begins with a disclaimer that it may be too scary for children.  It is the first Treehouse of Horror episode.  These episodes do not obey the show's rule of realism and are not treated as canon.  The opening disclaimer and a panning shot through a cemetery with humorous tombstones were features that were used sporadically in the "Treehouse of Horror" series and eventually dropped.  This is also the first episode to have the music composed by Alf Clausen, taking over for Danny Elfman who also wrote the show's theme. This is a list of "Treehouse of Horror" episodes produced by the animated television series "The Simpsons".  "Treehouse of Horror" episodes have aired annually since the second season (1990) and each episode has three separate segments.  These segments usually involve the family in some horror, science fiction, or supernatural setting and always take place outside the normal continuity of the show and are therefore considered to be non-canon. " Treehouse of Horror" episode aired on October 25, 1990 and was inspired by EC Comics Horror tales.  Before "Treehouse of Horror XI", which aired in 2000, every episode has aired in the week preceding or on October 31; "Treehouse of Horror II" and "Treehouse of Horror X" are the only episodes to air on Halloween.  Between 2000 and 2011, due to Fox's contract with Major League Baseball's World Series, several episodes have originally aired in November; as of 2011 every "Treehouse of Horror" episode has aired during the month of October.  From "Treehouse of Horror" to "Treehouse of Horror XIII", all three segments were written by different writers and in some cases there was a fourth writer that wrote the opening and wraparound segments.  For "Treehouse of Horror", there were even three different directors for the episode.  Starting with season fifteen's "Treehouse of Horror XIV", only one writer was credited as having written a "Treehouse of Horror" episode, and the trend has continued since. "Treehouse of Horror IX" is the fourth episode in the tenth season of the American animated television series "The Simpsons".  It first aired on the Fox network in the United States on October 25, 1998.  This is the ninth "Treehouse of Horror" episode, and, like the other "Treehouse of Horror" episodes, contains three self-contained segments: In "Hell Toupée", Homer gets a hair transplant and is possessed by the spirit of an executed criminal; in "Terror of Tiny Toon", Bart and Lisa are trapped in a special, extremely violent episode of "The Itchy & Scratchy Show"; and in "Starship Poopers", Marge reveals that Maggie is the product of a one-night stand with the alien Kang. "Gump Roast" is the seventeenth episode of "The Simpsons"’ thirteenth season.  It originally aired on the Fox network in the United States on April 21, 2002.  In the episode, Homer Simpson is honored by the townspeople at a Friars' Club Roast, until it is interrupted by Kang and Kodos.
Answer: Kang and Kodos