Question: "'Tis the Fifteenth Season" is the seventh episode of "The Simpsons"' fifteenth season, and the seventh Christmas-themed episode overall, this episode is notable as being the first to make reference to Lisa's Buddhism since she converted in which earlier Christmas episode, which is the sixth episode, of "The Simpsons"' thirteenth season?

Context articles: 'Tis the Fifteenth Season
You're Getting Old
How the Griffin Stole Christmas
A History Channel Thanksgiving
Blame It on Lisa
Today I Am a Clown
Smart &amp; Smarter
She of Little Faith
High School English
Hot Shots (Family Guy)

"'Tis the Fifteenth Season" is the seventh episode of "The Simpsons"<nowiki>'</nowiki> fifteenth season, and the seventh Christmas-themed episode overall.
 It first aired on the Fox network in the United States on December 14, 2003.
 This episode is notable as being the first to make reference to Lisa's Buddhism since she converted in an earlier Christmas episode, "She of Little Faith".
"You're Getting Old" is the seventh episode and the mid-season finale of the fifteenth season of the American animated television series "South Park", and the 216th episode of the series overall.
 It first aired on Comedy Central in the United States on June 8, 2011.
 In the episode, Stan begins to develop a profound sense of cynicism after celebrating his tenth birthday, where he is literally seeing everything as "crap".
 Meanwhile, Randy latches onto a new music genre, "tween wave," in an attempt to fit in, which causes problems in his marriage with Sharon.
"How the Griffin Stole Christmas" is the ninth episode of the fifteenth season of the animated sitcom "Family Guy", and the 278th episode overall.
 It aired on Fox in the United States on December 11, 2016, and is written by Aaron Lee and directed by Julius Wu.
 The episode's title is a play on the Dr. Seuss book "How the Grinch Stole Christmas!
" Unlike most episodes that are rated TV-14, this one is TV-PG.
"A History Channel Thanksgiving" is the thirteenth episode of the fifteenth season of the American animated television series "South Park", and the 222nd episode overall.
 It first aired on Comedy Central in the United States on November 9, 2011.
 In the episode, the boys accidentally uncover the true origins of Thanksgiving after watching a History Channel documentary alleging that aliens were present at the original harvest feast in 1621.
 It parodies the television series "Ancient Aliens", the 2011 film "Thor" and for-profit colleges.
"Blame It on Lisa" is the fifteenth episode of the thirteenth season of the American animated sitcom "The Simpsons".
 In the episode, the Simpson family goes to Rio de Janeiro, Brazil in search of a Brazilian orphan named Ronaldo whom Lisa has been sponsoring.
 Lisa used to receive a letter from Ronaldo every month, but that recently stopped and according to personnel at the orphanage, he is missing.
 As the Simpsons search through Rio de Janeiro, Homer is kidnapped and in order to free him the family must pay a ransom of $50,000, which they do not have.
 Lisa soon discovers that Ronaldo has been working in a flamingo costume on the children's television series "Teleboobies", which is the reason he left the orphanage.
 Ronaldo finally meets up with the Simpsons and gives them the $50,000 they need to rescue Homer.
"Today I Am a Clown" is the sixth episode of "The Simpsons"<nowiki>'</nowiki> fifteenth season.
 It originally aired on the Fox network in the United States on December 7, 2003.
 The episode focuses on Krusty's religion, Judaism.
"Smart and Smarter" is the thirteenth episode of "The Simpsons"<nowiki>'</nowiki> fifteenth season.
 It originally aired on the Fox network in the United States on February 22, 2004.
 When Maggie takes an IQ test, she is informed that she may be smarter than Lisa, who worries that her life will go nowhere.
 The episode was written by Carolyn Omine and directed by Steven Dean Moore.
 Simon Cowell also has a guest-voice appearance, playing the role of a brutally honest judge.
"She of Little Faith" is the sixth episode of "The Simpsons"' thirteenth season.
 It first aired in the United States on the Fox network on December 16, 2001.
 In the episode, Bart Simpson and his father Homer accidentally launch a model rocket into the Springfield church, causing the church council to accept funding plans from Mr. Burns for reparation.
"High School English" is the seventh episode of the fifteenth season of the animated sitcom "Family Guy", and the 276th episode overall.
 It aired on Fox in the United States on November 20, 2016, and is written by Ted Jessup and directed by Steve Robertson.
"Hot Shots" is the sixth episode of the fifteenth season of the animated sitcom "Family Guy", and the 275th episode overall.
 It aired on Fox in the United States on November 13, 2016, and is written by David A. Goodman and directed by John Holmquist.