A lot of the cast in fat friends later went on to star in either Gavin & Stacey or Early Doors.
Gaynor Faye's character Lauren mentions in the first season about filming an episode of Coronation Street and even mentions doing a scene with Rita Sullivan. Faye was previously in Coronation Street for four years playing Judy Mallett.
James Corden, Ruth Jones, Alison Steadman and Sheridan Smith later went on to star together in Gavin & Stacey