Shannon will be portraying Nancy, a single mother working as an associate producer for the talk show hosted by Maya Rudolph's character.
The actress made her Broadway debut last year as Marge MacDougall in Promises, Promises. Her many film and television credits include Saturday Night Live, Glee, Kath & Kim, Superstar, Bad Teacher, Sex and the City, and The Music Man. She also recently authored a children's book, Tilly the Trickster.
Up All Night also stars Christina Applegate and Will Arnett.