John Cho (born Cho Yo-han; June 16, 1972) is an American film and television actor and musician.
 He is best known as Harold Lee in the "Harold & Kumar" films; as the character John, MILF Guy No. 2, who popularized the term "MILF" in the "American Pie" films; and as the character Hikaru Sulu in the "Star Trek" reboot film series.
 Early in his career he also starred in the Asian-American films "Better Luck Tomorrow", "Shopping for Fangs", and "Yellow".
A Very Harold & Kumar 3D Christmas is a 2011 3D stoner comedy Christmas film directed by Todd Strauss-Schulson, written by Jon Hurwitz and Hayden Schlossberg and starring John Cho, Kal Penn and Neil Patrick Harris.
 It is a sequel to the 2008 film "Harold & Kumar Escape from Guantanamo Bay" and the third installment of the "Harold & Kumar" series.
 The plot follows Harold (Cho) and Kumar (Penn), two estranged friends who embark on an adventure to find a new Christmas tree after Kumar destroys the original.
Kalpen Suresh Modi (born April 23, 1977) is an American actor, producer, chef, and civil servant best known by his stage name Kal Penn.
 As an actor, he is known for his role portraying Lawrence Kutner on the television program "House", as well as the character Kumar Patel in the "Harold & Kumar" film series.
 He is also recognized for his performance in the critically acclaimed film "The Namesake".
 Penn has taught at the University of Pennsylvania in the Cinema Studies Program as a visiting lecturer.
Harold & Kumar is the name for a series of American stoner comedy films starring John Cho (Harold) and Kal Penn (Kumar).
 The first film, "Harold & Kumar Go to White Castle", was released on July 30, 2004, by New Line Cinema and spawned a sequel titled "Harold & Kumar Escape from Guantanamo Bay", released four years later. "
A Very Harold & Kumar 3D Christmas", the third installment of the series, opened nationwide in the U.S. on November 4, 2011.
David Krumholtz (born May 15, 1978) is an American actor.
 He played Charlie Eppes in the CBS drama series "Numbers".
 He played Seth Goldstein in "Harold & Kumar Go to White Castle" and its two sequels, "Harold & Kumar Escape from Guantanamo Bay" and "A Very Harold & Kumar 3D Christmas".
 He is also known for his role as Bernard the Elf in "The Santa Clause" and its sequel, "The Santa Clause 2".
 Additionally, he is known for his role as Mr. Universe in the 2005 film "Serenity" and played Michael the AV geek in "10 Things I Hate About You".
 In 2016, he provided the voice for Kareem Abdul Lavash in the adult animated film "Sausage Party".
Da'Vone McDonald is an American actor, best known for portraying "Dwayne the Bartender" in the successful 2008 romantic comedy "Forgetting Sarah Marshall".
 He has since appeared in brief roles in a number of films such as "Drillbit Taylor" (2008), "A Very Harold & Kumar 3D Christmas" (2011), and "The Five-Year Engagement" (2012) and has also guest-starred in various television series such as "House M.D.", "Raising Hope", and "Drunk History".
 Most of his roles are comedic in nature and, in several of his appearances, he has played bouncers and bodyguards.
Harold & Kumar Escape from Guantanamo Bay is a 2008 American stoner comedy film, and the second installment of the "Harold & Kumar" series.
 The film was written and directed by Jon Hurwitz and Hayden Schlossberg.
Todd Strauss-Schulson (born June 24, 1980) is an American film director, screenwriter, producer, editor, and cinematographer, best known for directing the 2011 comedy film "A Very Harold & Kumar 3D Christmas", and the 2015 horror comedy film "The Final Girls".
 He has also directed episodes of the television series "The Inbetweeners" (2012) and "Zach Stone Is Gonna Be Famous" (2013).
Julia Benjamin (born February 21, 1957) is a retired American film and television actress of the 1960s, 1970s and 1980s.
 She is best remembered for her character role as Susie Baxter, the daughter of Steve and Barbara Baxter and the first cousin of Harold "Sport" Baxter on the 1960s sitcom "Hazel."
 Benjamin was also well known for her roles in the movies "Mr. and Mrs. Bo Jo Jones" and "The Jordan Chance."
 Benjamin's career began at the age of eight on "Hazel" in 1965.
 "Hazel" was a sitcom that first aired in 1961 on NBC.
 The series centered on the Baxter family.
 The family included husband George Baxter, (Don DeFore), his wife Dorothy Baxter, (Whitney Blake) and their only child, son Harold "Sport" Baxter, (Bobby Buntrock).
 At the end of the 1964-65 television season, NBC canceled the series.
 CBS decided to pick it up for a fifth season.
 CBS cast Ray Fulmer, Lynn Borden, and Benjamin as George Baxter's brother Steve, his wife Barbara and their daughter Susie.
 The premise of the fifth season was that George and Dorothy had to move to the Middle East as part of a job promotion.
 So, Hazel and Harold moved in with Steve, Barbara, and Susie.
 The series was cancelled by CBS airing its last episode on April 11, 1966.
 It was never picked up again.
 After Hazel, Benjamin would only get roles in a limited few number of movies and guest starring roles on television.
 After Hazel went off the air, Benjamin would have only five roles in movies and television.
 Her television credits include three guest starring roles on the television shows "My Three Sons," "The Rockford Files" and "Riptide."
 Her movie credits include two TV movies; "Mr. and Mrs. Bo Jo Jones" (1971), and "The Jordan Chance" (1978).
 "Riptide" was Benjamin's last acting appearance.
 She has not acted in anything since.
Harold & Kumar Go to White Castle (alternatively known as Harold & Kumar Get the Munchies) is a 2004 American stoner comedy film and the first installment of the "Harold & Kumar" series.
 The film was written by Jon Hurwitz and Hayden Schlossberg, and directed by Danny Leiner.

Question: A Very Harold & Kumar 3D Christmas is part of what series?
Answer: the "Harold & Kumar" series.