"Friends" co-creator Marta Kauffman apologized in a recent interview for misgendering character Chandler Bing’s transgender mother during the show’s 10-year run.

"Pronouns were not yet something that I understood," Kauffman told the BBC in an interview scheduled to air on Monday. "So we didn't refer to that character as 'she.' That was a mistake."

Marta Kauffman attends the Los Angeles Special FYC Event For Netflix's "Grace And Frankie" on April 23, 2022, in Hollywood, California. (Jon Kopaloff/Getty Images)

She said she also regrets referring to the elder Bing character as "father" rather than "mother."

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"We kept referring to her as Chandler's father, even though Chandler's father was trans," she told the BBC.

In early seasons of the syndicated sitcom, references to Charles Bing, who also headlined a drag revue under the name Helena Handbasket, were relegated mainly to one-liner jokes like one from the first season in 1995 when Chandler (Matthew Perry) said: "If I turn into my parents, I'll either be an alcoholic blond chasing after 20-year-old boys, or I'll end up like my mom."

By season seven, however, as Chandler and Monica Geller (Courtney Cox) prepared to get married, the two traveled to Las Vegas to meet his estranged parent at her drag revue and invite her to the wedding.

Actress Kathleen Turner played Chandler’s transgender mother while Morgan Fairchild appeared several times as his biological mom.

Kathleen Turner during the opening night curtain call for "Kathleen Turner: Finding My Voice" on Broadway, Dec. 16, 2021, in New York City. Turner played Chandler Bing's transgender mom on "Friends." (Bruce Glikas/Getty Images)

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In a scene between Fairchild and Turner at Monica and Chandler's wedding reception, Turner's character accuses Fairchild's character of being too old to wear her low-cut dress, causing Fairchild to fire back, "don't you have a little too much penis to be wearing a dress like that?"

The show never actually used the word transgender, referring instead to Charles as gay and a drag performer who would also wear women's clothes outside of drag shows.

"People thought Charles was just dressing up," Turner told the Gay Times of the character.

The cast of "Friends": Lisa Kudrow as Phoebe Buffay, Matt LeBlanc as Joey Tribbiani, Courteney Cox Arquette as Monica Geller, Matthew Perry as Chandler Bing, Jennifer Aniston as Rachel Green, David Schwimmer as Ross Geller. (Reisig & Taylor/NBCU Photo Bank/NBCUniversal via Getty Images via Getty Images)

Turner appeared three times in season seven in 2001, including Monica and Chandler’s wedding, and said in 2018 that she would not have taken the role today since a real trans woman could play it now.

Kauffman said she recently fired someone for making a joke about a transgender camera person.

"That just can't happen," she said.

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Kauffman also said she regrets not having enough diversity on the mostly White show, admitting she was "clearly part of systemic racism in our business."

"I was unaware of that, which makes me feel stupid," she said. "That was a very valid, extremely difficult criticism which still... I get emotional about."

Kauffman, who also created the Jane Fonda and Lily Tomlin show "Grace and Frankie," said, "If I knew then what I know now, there are certain things I would have changed. But I didn't know them and I have since learned."

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She also pledged last week to donate $4 million to her alma mater, the Boston area’s Brandeis University, to establish an endowed professorship in the school’s African and African American studies department.