Mister Justin
From 1971 to 1976, Burt Mustin appeared in five episodes where his first appearance was as a night watchman, and then he did an additional four appearances as Justin Quigley, a feisty octogenarian.
Meathead
In the show, Archie often refers to Michael by the nickname “Meathead”, but there is a later episode where Archie Bunker himself was known as “Meathead” in his youth.