Mammy's Ass is the first Christmas special of the comedy Mrs Brown's Boys and was first broadcast on 26th December 2011.
Agnes is stapling decorations up and explains that Trevor will be coming home from the Mission. Winnie enters and explains that she hasn't got enough money to purchase Jacko's medicine and that she hasn't any idea about what she will do about it. She manages to get a job as a consumer advocate for a magazine which sends her products for her to try out.
Maria gets ready to go to work and Dermot comes dressed as a reindeer. Hillary Nicholson also enters and explains that Christmas dinner is at her house. Buster also shows 'the deal of the century' to Agnes. Chocolate Kimberley biscuits for 2 Euro a tin, but got 2,000 tins for 50 cent a tin. The turkey that Agnes is going to buy off Buster will be 50 Euro but instead he delivers it while still alive. He reads the instructions for killing a turkey and one of the instructions is to place a bag over the turkey and kill it when it can't see anything. But Buster puts the bag on his own head and damages half of the exterior door; it is not known what became of the turkey after this.
Meanwhile, Agnes auditions for the Christmas Nativity, hoping to be cast as Virgin Mary, but she is instead cast as a cow. Also, while the Brown children are talking to Trevor on Facebook, they learn he can't make it home and they try to figure out how to break the bad news to their mother, but its Dino who ultimately lets the cat out of the bag. Agnes later reads some Christmas letters to the family including Rory and Trevor's letters. Hillary enters with a Chocolate Kimberley box. Agnes turns on her lights and the special ends with Maria singing Silent Night. Agnes does not notice that Trevor has walked in. When she turns around and sees Trevor, she embraces him whilst crying with joy.
- Brendan O' Carroll as Agnes Brown
- Dermot O' Neill as Grandad
- Ellish O' Carroll as Winnie McGoogan
- Fiona O' Carroll as Maria Brown
- Paddy Houlihan as Dermot Brown
- Susie Blake as Hilary Nicholson
- Danny O' Carroll as Buster Brady
- Jennifer Gibney as Cathy Brown
- Rory Cowan as Rory Brown
- Amanda Woods as Betty Brown
- Pat Shields as Mark Brown
- Susie Blake replaced Sorcha Cusack playing the part of Hillary Nicholson and will do for the rest of the future episodes.
- Agnes (unlike so many others) staples her Christmas decorations to the wall instead of sticking them.
- First appearance of Trevor Brown, though he doesn't speak in this episode.
- Sharon McGoogan appears as a background character in this episode. Her first proper appearance is in the next episode, Mammy Pulls it Off.
- Mick and Father Quinn do not appear in this episode though they are both listed in the closing credits on the DVD release. Recent repeats have edited this error out.
- The song that Grandad sings when Agnes is hitting him over the head to try out the crash helmet Winnie was sent is (Ghost) Riders In The Sky by Johnny Cash.
- Maria sings for the first time in this episode; she will do so again in The Virgin Mammy, and again in Buckin' Mammy.
- On December 5th 2013, a repeat of this episode was interrupted by the announcement by Jacob Zuma, President of South Africa, that Nelson Mandela had passed away. The BBC received 1,300 complaints from viewers, some of whom took to Twitter to voice their disappointment that their entertainment had been interrupted.
- Grandad: (about the turkey) What's he doing here alive?
Agnes: I'm sure he's looking at you thinking the same feckin' thing.
- Agnes: (on being cast as a cow instead of the role she auditioned for) From the Virgin Mary to the dairy.
- Agnes: (reading a book with some family letters to Santa Claus) Here's one of Rory's letters. He was only ten. Listen to this "Dear Santa, sir or madame, please could I have an embroidery set?". Oh, Cathy Brown!
Agnes: You were such an angry child. "Dear red-nosed fat bastard!" (She turns the page) Here's Trevor's. "Dear Santa, please don't bring me anything. Give my present to a poor boy who has no toys".
Dermot: That would be Trevor, alright.
Agnes: Yes, Dermot, that would be Trevor. He'd give them away, and you'd fuckin' steal them back.
- (Post-credits) Agnes: You see? There is a Santa Claus.