Mrs. Brown's Boys is a British-Irish award winning sitcom created by and starring writer and performer Brendan O'Carroll. The show is based on O'Carroll's stage plays about the character Agnes Browne, which were developed from books and straight-to-DVD films. The sitcom continues the stories of Agnes, now with the shortened surname "Brown", and her family who are played by real life close friends and family of O'Carroll's. After being slated by critics, the show has become a ratings success in both Ireland, where it is set, and the United Kingdom, where it is recorded. On 29 December 2012 the show began its third series. Mrs Brown's Boys is a co-production among BBC Scotland, BocPix and RTÉ.
"Slasher Sam" is a murderous split personality trope.
He's an escaped prisoner, who takes hostages and attempts to murder people. They use the we pronouns in refering to themselves, and there are arguments back and forth between themselves, with the stereotypical looking in one direction for one persons voice, looking the other way for the other person talking.
It doesn't go in much depth, but the whole episode basically revolves around the character(s). And the multiplicity / plurality is clearly used simply as a plot device to make the audience unsettled so the Slasher Sam seem more like a criminal.