Rich Man, Poor Man (1976)

S5E10 Peter's Two Dads

Following the death of Peter's father, Francis, Thelma reveals that Peter's biological father resides in Ireland. Eager to find him, Peter and Brian travel there, only to discover that his dad is the local alcoholic. To establish their connection, they engage in a drinking game. Meanwhile, Stewie misbehaves, leading Lois to spank him. Discovering that he enjoys the punishment, Stewie starts to act out even more, seeking trouble to earn another spanking.