Biff was born on March 26, 1937 in Hill Valley, California. He
is the great grandson of Buford 'Mad Dog' Tannen. He is not very
bright and only got through high school by bullying George McFly to
do his homework for him. Biff is feared by most of his schoolmates.
He is less brave when he is without his gang. He also has a crush
on Lorraine Baines and constantly refers to her as "my girl."
Lorraine does not return the sentiments.
By 1985, Biff's marital status is unknown – no mention of a wife
or children was ever made in the trilogy, although Biff has a
grandson Griff by 2015, suggesting that Biff had at least one child
by 1985. The animated series reveals that Biff has a son, Biff Jr,
although this is not taken as canon by many fans. A draft script
reveals that his middle initial is "H", although his middle name
was never mentioned in the trilogy. Also, a BTTF comic showed a
"Mugsy Tannen" living in 1920's Prohibition-era Chicago as a gang
boss, probably Mad Dog's son.
Biff is noted for malapropisms: for example, he thinks the
saying is "make like a tree and get out of here" instead of "make
like a tree and leave." His attitude is to do something rather than
think things over and he has no problems with using his fists to
get what he wants. Biff will try and get out of paying for things
if he has to and is looking for a nice easy life where everyone
else will do things for him. He also likes cars and ends up with a
career waxing and cleaning them with his auto detailing business.
Biff is still a bully, but can be nice and/or charming when he
needs to be, usually to get out of trouble. Also, as the trilogy
unfolds, we discover Biff has a strong dislike of manure.