Mary Halloran is a minor character that appeared on Glee in The Untitled Rachel Berry Project. She is a writer that visits Rachel and her friends in New York to write a pilot for a television show about Rachel Berry.
She is portrayed by actress Kristen Schaal.
At the opening of the episode Rachel, Mercedes, Kurt, Blaine, Artie, and Sam are all in the Bushwick apartment having Monday night dinner. Rachel tells them that Mary will be joining them so that she can learn the essence of Rachel's character and write a script for a movie pilot about Rachel. Kurt doesn't like the idea of someone crashing Monday night dinner. Then there is a knock on the door and all of the friends gather thinking that it is Mary, but then Brittany comes in and everyone is happy to see her. After Brittany comes in, Mary walks into the apartment. She introduces herself and then says that the smell of Chinese food gives her the "Lady Die's". Rachel shakes her hand and introduces herself and then attempts to introduce Mary to her friends, but Mary says don't bother because she never remembers people's names. After some more awkward conversation, she asks to go to the bathroom and says that she is so excited to be working with Randy (talking to Rachel).
Next, Mary is on the floor typing on a typewriter while asking Rachel about herself. Rachel says she has two gay dads and then Mary writes that Rachel has two gay NASA dads. She writes that Rachel is lazy when Rachel says that eight shows a week on Broadway can be kind of tiring. After a lot more awkward conversation, Mary once again asks to go to the bathroom, but not to use it to snoop through it.
Later, Mary is seen interviewing Artie. He gets frustrated at her when she is trying to touch his computers and when she puts a donut in her bra. Then, she is seen interviewing Blaine while laying at his feet. Blaine asks her if she is an actual writer from a real television network. She responds with gibberish. Brittany then tells her that she is a breath of fresh air and that she loves Mary's pajamas. Mary tells Brittany not to steal her pajamas because little mousey's live in the pocket and that a kitty lives in her pants.
Kurt tells Rachel that Mary is insane and Brittany tells Rachel that Mary is great. Kurt goes on to tell Rachel that she needs to trust her own instincts not crazy Mary's.
After the first read though of Mary's script, Rachel decides that it makes no sense and that if she is going to do this she needs to do it her way or no way at all.
Later, Mary and Rachel are at the Spotlight Diner talking about the show. Rachel tells Mary that the script isn't really about Rachel's true self. Rachel then sings Glitter in the Air as a way to show Mary her true essence. Mary doesn't like this idea at first, but then at the end of it tells Rachel that watching her sing made her happy and that has never happened to her before. Mary says that she will give Rachel's version a shot.