To unlock NFC Hall of Fame, AFC Hall of Fame, Dummies, Glaciers, Deceivers, and Tridents, you must defeat them in Fantasy Challenge mode. They will be under the final league, called the Supreme League. Once you beat them, you can play with them in Play Now mode. The easiest way to beat the Supreme teams is to change the difficulty to Rookie or Pro. Another way to unlock the Hall Of Fame teams is to buy their Madden cards, which appear randomly when you purchase cards for 100 tokens.