In season 1, episode 14 of 30 Rock, Liz Lemon is called the c-word by TGS writer J. D. Lutz, which she is rightfully outraged by. She then warns the staff that using that "horrible word" will result in job termination. It has been long known that the incident in the show was inspired by one of Tina Fey's experiences in real life, but until now there were no details regarding who called her that, or during what show.
Today Fey told Howard Stern it was Colin Quinn, back when she was a writer for SNL—at the time, Colin Quinn was a Weekend Update anchor.
She told Stern, "I love him so much. I was trying to help him with a show that he was working on, and I think his anxiety about the writing of the show spilled over. It was very random. I was like, ‘What?!’ He left me a message and he said that. I couldn’t even guess why. Usually, if someone calls you that, you’re like, ‘I know what I did.' I asked Colin to be on 30 Rock like three times after that, and he turned us down every time. I saw him on Girls and was like, 'He's dead to me.'" But the two have since made up, Fey says—"We've since reconnected, at the SNL 40th, actually, and we're good."
UPDATE: Colin Quinn has tweeted in response: "Statement: It's all true. I have used profanity when I've been angry at people. When I was wrong ( as with Tina) I've said sorry to them."
Statement: It's all true. I have used profanity when I've been angry at people. When I was wrong ( as with Tina) I've said sorry to them.
— Colin Quinn (@iamcolinquinn) December 14, 2015