*SPOILER (If you haven't seen the latest ep (this means you, England))*
Peter Griffin - Husband, Father...Brother: In researching his heritage, Peter's Great-Grandfather, Osias Griffin, is one of the owners of a dozen cutting-edge-technology telephones. His Great-Grandfather, Thomas Griffin, was apparently a philosopher ("Why?"). An unknown amount of generations back (described as "In 1840"), Nate Griffin is found to be an African-American slave.
All of these characters are assumed to be American, correct? American telephones, American accents, American slave, and all supposedly in a straight father-son line down to Peter. However, Peter's father (in Holy Crap!) was obviously raised in Ireland. Sure, someone coulda jumped on a boat from America to Ireland and then Peter's dad came back, but as Thomas Griffin would say... "Why?"