In Derry Girls Joe McCool, Mary and Sarah's father, and Erin and Orla's maternal grandfather, has lived with the Quinns since his wife died. Joe shows nothing but contempt for Gerry, constantly criticising him and encouraging Mary to leave him.
JOE MCCOOL: Why can't you just leave my Mary alone?
Has any in-episode dialogue or commentary from the creators ever explained what Joe McCool's problem is with Gerry Quinn?