At the final basketball game, Jon & Ponch wear game jerseys with their call sign numbers on them- Jon with a 3 for 7 Mary 3 and Ponch with a 4 for 7 Mary 4. None of the other characters have a jersey with a corresponding ID number.
Frank tells his wife Muriel that when he looked in the trailer and she wasn't there he aged 20 years. The actor playing Frank, Jack Kruschen, was 18 years older than Beverly Sanders, who plays Muriel.