One detail from the past that sullies its perfection is the memory of Biff stealing a football from the school. Biff is the star of the team, yet he is also developing traits that will later lead him to trouble.
Biff's petty theft demonstrates his elevated sense of self, his feelings of entitlement and false grandeur. These qualities match those of his father and show the reader that Willy's treatment of Biff is certain to lead to a destructive arrogance in his son.
Biff's friend Bernand recognizes the danger in Biff's theft and attempts to curb Biff's behavior, but Willy's influence is seen here too as Biff shrugs off Bernards warnings and Willy does too.
According to Willy, however, Bernard is the one who will fail at life because he is not popular...