The Virgin Mammy is the second of two Mrs Brown's Boys Christmas specials to be screened in December 2012.
Agnes has finally been granted permission to stage her own version of the Nativity, and she has written a script entitled Men Are Bastards, but several changes are made to the script, including the title and some of the dialogue, and Agnes is told by son Trevor she can't use the baby cannon she had got for the birth scene. Agnes is also having trouble with her wrist suffering from rheumatism. Buster gives her a magnetic bracelet intended for animals, but it soon starts to cause mayhem when it becomes attached to anything metal - including the camera. To make matters worse, Buster doesn't have the key to remove the bracelet, so Agnes is stuck wearing it until New Year.
In spite of the magnetic bracelet, Agnes still plans to put on the Nativity with Hilary, who is dressed as Cleopatra, as the narrator. However, from the moment the curtain goes up, things start to go wrong as one disaster after another befalls the production: the audience laughs at Agnes in the role of the Virgin Mary, everyone messes up their lines, Buster is accidentally set on fire and then is knocked unconscious when he is hoisted up and hits his head, the Three Kings (Mark being one of them) are all dressed as Elvis Presley, Grandad substitutes for Dino as the front half of the "donkey-zebra" and farts in Rory's face, and Hilary faints.
When it is realized that they don't have a baby to play the Baby Jesus, Agnes improvises and has Grandad act the part, then even tries to breast-feed him. This is the last straw for Cathy, who fires her mother from the play and stages a production she and Maria had devised with Betty as the Virgin Mary and the Nativity becomes a success. Agnes' magnetic bracelet then causes her to accidentally get attached to Father Damien's belt buckle. When she tries to pull away, she ends up ripping off his trousers. The episode ends with Agnes on stage, talking to an empty theatre.
- Bono can be seen as one of the angels.
- The song that Maria sings is A Spaceman Came Travelling by Chris de Burgh.
- Dermot spends most of the episode dressed as the Genie of the Lamp except for one scene where everybody is getting ready for the Nativity where he is dressed in civilian clothing.
- Father Damien: (reading the title of Agnes' script) Men Are Bastards?
Agnes: It's just a working title.
Cathy: Mammy, seriously?
Agnes: Well it was a man who wouldn't give them a room. Herod was a man. Joseph was a man and he never booked a room in advance.
- Trevor: You can't go launching the Baby Jesus from a cannon.
- Agnes: (after seeing Hilary dressed as Cleopatra) You never have an asp when you need one.
- Hilary (as the Narrator): "It was over two-thousand years ago and the world was in an awful state altogether". I didn't write this. "In the small village of Nazareth ..."
The curtains pull back to reveal Agnes as the Virgin Mary lying on a bed as the audience applauds.
Hilary: "... lived a young virgin".
The audience laughs.
- Buster (as the Angel): I am the Angel Michael, and I come with a message from above. You are with child, and it is a very special child.
Agnes (as the Virgin Mary): But this cannot be, for I am a virgin.
The audience begins to laugh.
Agnes: (breaking character) Hey!
- Cathy: (after discovering Grandad is playing the Baby Jesus) Jesus Christ!
Agnes: What a wonderful name! We shall call him that!