Peter's Two Dads

S5, E10: After Peter's dad Francis dies, Thelma tells him that his real father actually lives in Ireland. Peter and Brian head there in search of his father, who they discover is the town drunk, and they play a drinking game to prove his paternity. Meanwhile, Stewie acts out and Lois spanks him. Realising that he likes being spanked, Stewie does whatever he can to get into trouble.