Erin Hunnicutt is the infant daughter of 4077th MASH surgeon, Captain B.J. Hunnicutt, and Peg Hunnicutt. Frequently mentioned in various episodes, she is seen in "Oh, How We Danced" in a home movie which Peg had sent to B. J. as a wedding anniversary and in a still photograph with Peg Hunnicutt in "Where There's a Will, There's a War". The home movie was in black and white and the child actors who played the part were twins Michelle and Jennifer Scott. Earlier, in "Period of Adjustment", B. J. was very upset to hear from Peg that when Erin had called Radar "Daddy" when Peg and Erin had gone to receive the homecoming Radar at the airport.
The character's first name "Erin" is named after Erin Elizabeth Farrell, the actual daughter of Mike Farrell and his first wife Judy Farrell.