Francis Griffin was the stepfather of Peter Griffin and ex-husband of Thelma Griffin. Due to being a devout Irish-American Catholic the relationship over the years had been rocky. However, he did love Peter, though he did not like him. Francis is extremely religious and honors Jesus, God and the Pope. However, he was extremely stubborn with his views. On the wedding day, he taped a sign saying "To A Protestant Whore" underneath the "Just Married" sign on back of the limo. To a lesser extent he despised Lois for her German heritage, and was angry at Peter for not marrying an "Irish rose". He also hit Brian with his Bible for questioning and mocking him. When the Pope was fine with Peter's interfaith marriage to Lois and tries to convince Francis to accept Peter's marriage, Francis deems the Pope to be an untrue Catholic as seen in "Holy Crap". The Pope would eventually hire him as a special assistant at the end of the episode, as Francis was forced to retire from the Pawtucket Mill earlier in the episode. All Francis believed in was work, but eventually settled in a retirement home.
In "The Father, the Son, and the Holy Fonz", he baptizes his grandson Stewie with tainted holy water. When Peter starts the Church of the Fonz, he finds it extremely stupid. He even resorts to collaborating with Brian on sabotaging the religion. Afterwards, it was revealed he was the lone remaining follower of Fonzism.
In "Peter's Two Dads", he attends Meg's birthday party, bringing her a cookie from the retirement home as a present. A drunken Peter falls on him while riding a unicycle, mortally injuring him. He suffered crushed ribs, busted spleen and a punctured lung. His final words were "Peter, you're a fat stinkin' drunk!” After Peter goes to a therapy session, it was revealed that Francis was not Peter's biological father, but an Irishman named Mickey McFinnigan. A series of memories show Francis constantly told Peter this. His ghost helps remind Peter that he is a “fat stinking drunk”, which helps Peter realize a way to convince McFinnegan that he really was his son.
His ghost reappears in "Family Goy", telling Peter to stop embracing Judaism.
- Francis' death was the first event to make the Stewie Griffin: The Untold Story timeline void.
- Francis hates Lois just as Carter Pewterschmidt hates Peter. He also dislikes Brian because of his atheism, although he did work with him to put some sense into Peter in "The Father, the Son, and the Holy Fonz".
- In "Peter's Two Dads", both Lois and Brian were overjoyed that Francis was dead and expressed their happiness on the front lawn of their house behind Peter's back.
- While he is shown to dislike Lois being Protestant, most episodes imply that she converted to Catholicism. In "Big Man on Hippocampus", Lois mentions having a rosary, and episodes like "Boys Do Cry" show Lois taking part in Catholic sacraments.
- In multiple episodes, Peter talks about his relatives and ancestors, all of which share the name Griffin, not McFinnigan. This makes little sense seeing that all these relatives have almost perfect resemblance to Peter. It is conceivable that the Griffins and the McFinnegans share a common ancestor, especially since Nate Griffin, Peter Griffin and Mickey McFinnigan all look practically identical in shape and size.
- Peter mentions that his father was a WWII veteran in "The Old Man and the Big 'C'".
- Peter tries to wipe his memory of being at a couples retreat in the Bahamas in "Take My Wife" by hitting himself on the head with a coconut, but instead remembers that he was abused by his dad.
- Peter also notes that his parents allowed his sister Karen Griffin to bully him in "Peter's Sister".
- FG202 "Holy Crap"
- FG415 "The Perfect Castaway" (seen at Peter's funeral)
- FG418 "The Father, the Son, and the Holy Fonz"
- FG425 "You May Now Kiss the...Uh...Guy Who Receives" (cameo at Jasper's wedding)
- FG430 "Stu & Stewie's Excellent Adventure" (cameo at Chris' wedding)
- FG502 "Mother Tucker" (mentioned)
- FG510 "Peter's Two Dads" (dies in this episode)
- FG802 "Family Goy" (as a ghost)
- FG1318 "Take My Wife" (mentioned)
- FG1402 "Papa Has A Rollin' Son" (mentioned)
- FG1406 "Peter's Sister" (mentioned)
- FG1411 "The Peanut Butter Kid" (mentioned)
- FG1607 "Petey IV" (mentioned)