At one point, Al bumps into Scooter's shoulder instead of passing through him.
Sam wears multiple numbered jerseys. A hotshot college football player would wear only his own jersey.
Elisabeth says she does not know who Abbie Hoffman is. While Hoffman became much more widely known in the summer of 1968 and the subsequent trial of the Chicago 7, he was an anti-Vietnam war activist and national figure by 1967, and a campus protest organizer against the Vietnam War would certainly have known of him.
When Sam and Al are talking on the path, a girl in a lime green dress is walking behind them. The camera angle changes and the same girl walks right past them.
The Bally pinball machines in the frat house, Amigo and Delta Queen, were released in 1974. The other pinball machine, a Williams Travel Time, was released in 1972.