In 2014, it emerged that Macaulay Culkin, who played her on-screen son in Home Alone (1990), still calls her "Mom".
She delivered a tearful eulogy at John Candy's funeral.
She has a congenital condition called "Situs Inversus", in which the chest and abdominal organs are arranged in a perfect mirror image, the exact reverse of their normal positions. Most people with situs inversus experience no medical symptoms or complications from the condition, and it occurs in fewer than 1 in 10,000 people.
Her acting mentor was the comedian Gilda Radner.
John Candy, her longtime collaborator, died on her 40th birthday.
She frequently appears in Tim Burton's films. He directed her in Beetlejuice (1988) and Frankenweenie (2012), and she voiced a role in The Nightmare Before Christmas (1993), which Burton produced. She also appeared in Lemony Snicket's A Series of Unfortunate Events (2004), which he decided to direct.
She has known Eugene Levy since their days on SCTV (1976), and has known Dan Levy since he was a baby.
In 2013, she joined "Danny Elfman's Music from the Films of Tim Burton" to perform "Sally's Song" from The Nightmare Before Christmas (1993). She received a standing ovation both as she came on stage and as she left it.
She is depicted on one of a set of five Canadian commemorative postage stamps, issued on August 29, 2014, honouring Great Canadian Comedians, with no denomination specified. In addition to the main portrait, she is shown in her roles as Delia Deetz in Beetlejuice (1988), Marilyn Hack in For Your Consideration (2006) and Mickey Crabbe in A Mighty Wind (2003). Others honoured in the set include Jim Carrey, Mike Myers, Martin Short and Olivier Guimond. Each stamp was priced at 85¢ on its issue date.
In June 2007, she received a star on Canada's Walk of Fame.
After casting Macaulay Culkin, Joe Pesci and Daniel Stern for Home Alone (1990), Chris Columbus felt confident enough to cast actors with growing followings such as O'Hara, after seeing her work on SCTV (1976) as well as John Heard, and Tim Curry and Rob Schneider in Home Alone 2: Lost in New York (1992), because they were all open to the films.
She shares a 40-year acquaintance with Eugene Levy; they have appeared together in many projects: SCTV (1976), SCTV Network (1981), SCTV Channel (1983), Nothing Personal (1980), The Last Polka (1985), Double Negative (1980), I, Martin Short, Goes Hollywood (1989), Waiting for Guffman (1996), Best in Show (2000), Over the Hedge (2006), For Your Consideration (2006), A Mighty Wind (2003) and the May 5, 1975 (1975) episode.
She was a naturalized US citizen.
She learned to play the autoharp for her role in A Mighty Wind (2003).
Tim Burton's wedding gift to her and Bo Welch was two tickets to a private tour of the Vatican.
After her years as a regular on SCTV (1976), she earned the title Queen of Comedy. Catherine O'Hara has an almost religious cult following worldwide.
In 1973, she began working as a waitress at "Second City" in Toronto. Her brother Marc O'Hara and her sister Mary Margaret O'Hara also worked there.
She has appeared in two films selected by the Library of Congress for the National Film Registry as "culturally, historically or aesthetically" significant: Home Alone (1990) and The Nightmare Before Christmas (1993).
As seen on SCTV (1976), she does a perfect impression of Katharine Hepburn.
Two holiday classics she stars in, Home Alone (1990) and The Nightmare Before Christmas (1993), are re-released in cinemas worldwide every December.
Together with her sister Mary Margaret O'Hara and her friend Robin Duke, she composed two songs she performed in The Last Polka (1985).
Macaulay Culkin's speech at his Hollywood Walk of Fame star ceremony in 2023 moved her to tears.
She has a country house in Muskoka, Ontario (with her husband Bo Welch).
She met her husband Bo Welch on the set of Beetlejuice (1988), where he worked as production designer.
She is a third-generation Irish/Canadian/Catholic.
She was part of the Northern Lights group that sang "Tears Are Not Enough", a track included on the "We Are The World" album.
She wrote SCTV's (1976) famous sketch "High-Q", considered one of the funniest sketches in SCTV (1976).
She turned down a part in Mascots (2016), directed by her frequent collaborator Christopher Guest, because of a scheduling conflict with Schitt's Creek (2015). It was the first film she had not starred in since The Big Picture (1989).
She attended the same high school as her fellow Canadian entertainer Dave Foley.
She appeared in two unconnected adaptations of Daniel Handler's "A Series of Unfortunate Events" book series: as Justice Strauss in A Series of Unfortunate Events (2004) and as Dr. Georgina Orwell in A Series of Unfortunate Events (2016).
She appeared in three films with Joe Pesci: Betsy's Wedding (1990), Home Alone (1990) and Home Alone 2: Lost in New York (1992).
She is a high school friend of Robin Duke from Burnhamthorpe Collegiate in Etobicoke, Ontario, Canada. They first appeared together in a school production of "Harvey".
She was awarded the O.C. (Officer of the Order of Canada) on May 11, 2017, and was invested by the Governor General of Canada on November 20, 2018.
In 2024, she was invited to join the actors branch of the Academy of Motion Picture Arts and Sciences (AMPAS).
She auditioned for the role of Jane Craig in Broadcast News (1987). Holly Hunter was cast instead.
Janeane Garofalo stated that Catherine O'Hara had a significant influence on her acting career.
Luke Perry died on Catherine's 65th birthday, and her close friend and fellow SCTV alumnus John Candy died on her 40th birthday.
Since the category was created in 2002, she has voiced characters in five films nominated for the Academy Award for Best Animated Feature. These films are the English dubs of Monster House (2006), Frankenweenie (2012), When Marnie Was There (2014), Elemental (2023) and The Wild Robot (2024).
She auditioned for the role of Susan in Big (1988), a film that Robert De Niro was involved with.
After her death, she was buried in Holy Cross Cemetery in Culver City, California.
It was based in Toronto, Ontario, Canada and Beverly Hills, California, USA.