Fintan Stack is a obnoxious, rude and destructive priest who was sent to the parochial house as Jack's replacement, after he contracts "Hairy Hands Syndrome". He was played by Irish comedian Brendan Grace.
Stack torments Ted and Dougal by driving Ted's car into a large wall, telling him all about it and saying the only thing important was that he liked it, insulting Ted and his friends in the priesthood (threatening to shove one's head through a wall), forcing Dougal to get drunk on Jack's whiskey (he didn't have Ted's permission to do so), eating Ted's Frosties, drilling holes in the living room wall and blasting Jungle Music at 3:00 in the morning.
Fed up with Stack and his rude antics Ted and Dougal break Jack out of St Clabbert's and return him to the parish house. Upon returning Jack becomes enraged when he discovers that Stack has given his entire alcohol hoard to Dougal. Before he can attack Stack, however, it is discovered that Stack himself has also contracted the Hairy Hands Sydrome from Jack's rotting and unsanitary chair. Stack is then sent to St. Clabbert's Hospital.