When a townmember, Frank, gets evicted from his home he finds a bond issued to his grandfather over 100 years ago. Andy realizes because it was an $100 bond with an 8.5% interest rate compounded annually, Frank might just be rich.
Kramer gives Elaine an organizer that he got at the bank when he opened a new account; Jerry proudly shows off a tape recorder that he got at a different bank. In the days before bank deregulation, interest rates were administered: 0% on checking accounts, 5.25% on savings accounts. With market interest rates higher than these, there was no way for banks to compete for funds except to offer additional perks like toasters, tape recorders, and organizers.
Fry experiences the effects of compound interest on his savings. He started with 93 cents in his bank account 1,000 years ago, and it has had an average 2.25% interest rate over the 1,000 years. Fry learns that he is now a billionaire.