Marta Kauffman has admitted that Friends bosses made a "mistake" by using the wrong pronouns to describe a transgender character.
In the show, Chandler Bing's parent is referred to as his "dad" despite identifying as a woman and co-creator Kauffman has insisted bosses on the show should have done better but errors were made because of a lack of understanding at the time.
Speaking on BBC World Service, Kauffman said: "We kept referring to her [Chandler's transgender parent] as 'Chandler's father', even though Chandler's father was trans.
"Pronouns were not yet something that I understood. So we didn't refer to that character as 'she'. That was a mistake."
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This is the second "mistake" Kauffman has admitted making during the show's creation.
The executive producer apologised last week for the lack of diversity in the show and pledged US$4 million ($6.4m) to her alma mater Brandeis University, in an attempt to make amends.
Kauffman discussed the show's lack of diversity, which has attracted plenty of criticism over the years - describing the comments as "valid" and insisting she "feels stupid" for not recognising the problems.
She said: "Friends has been criticised in a number of ways. The biggest one being that we did not have enough representation of black people. And over the course of the last few years I've gotten to the point where I can say unfortunately yes, I am guilty of that.
"And I'll never make that mistake again. I was clearly part of systemic racism in our business. I was unaware of that, which makes me feel stupid.
"That was a very valid, extremely difficult criticism which still I get emotional about. 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."