Buford Howard "Biff" Tannen is the main antagonist of the Back to the Future franchise, with his 1955 self serves as the main antagonist in Back to the Future and Back to the Future Part II, while his 1985 self serves as a supporting antagonist in Back to the Future, a minor antagonist in Back to the Future Part II, and the overarching antagonist in Back to the Future Part III, his 1985A self serves as the main antagonist of Back to the Future Part II, and his 2015 self serves as the overarching antagonist in Back to the Future Part II.
Biff was the great-grandson of Buford "Mad Dog" Tannen. He was not very bright and only got through high school by bullying George McFly to do his homework for him. Biff often took pleasure in calling George an "Irish bug", and regularly bullying and tormenting him. He was feared by most of his schoolmates. The only person he recognized as an authority figure was Mr. Strickland, his high school disciplinary officer. In 1955, he surrounded himself with a gang consisting of Match, Skinhead, and 3-D.
By 1985, Biff's marital status is unknown, although Biff had a grandson Griff by 2015, meaning that Biff had at least one child by 1985. (According to some sources, Biff had a son, Biff Jr., who, it is suggested, owned the Cafe 80's). He may have also had a daughter named Tiff Tannen, short for Tiffany.
Biff was notorious for mixed metaphors. For example, he said "make like a tree and get out of here" instead of "make like a tree and leave" on more than one occasion. He also once said "That's about as funny as a screen door on a battleship" instead of submarine. During his theft of the DeLorean in 1991, he said "Have a nice trip, see you next winter!" His insult of choice was "butthead", or — usually when addressing George McFly — (Irish) "bug." One of his routines was to knock on someone's head and say "Hello? Hello? Anybody home?" He liked cars and ended up with a career waxing and cleaning them with his auto detailing business. Biff was still a jerk and more passive-aggressive than a bully, but could be nice when necessary, usually to get out of trouble.
He is also one of the main causes of the timeline occurrence of 1985A (or 1985Alternate, OR also Alternative 1985) due to him using the time machine DMC vehicle along with Marty McFly due to him purchasing the Gray Sports Almanac which Biff later discovered.