Actor Tristram Coffin appears in this episode as the Ambassador. Coffin was featured in many of the classic cliffhanger serials that inspired this television series, including the original Batman (1943) serial itself (which a revival of in the '60s caused the TV series to be born), wherein he was featured as one of the villain's main henchmen. He was also the first actor to don the famous "flying suit" as the eponymous serial crime fighter King of the Rocket Men (1949), which would later serve as an inspiration for The Rocketeer (1991).
The Riddler's henchmen are the River Rats Gang. Later in 1966 this episode's director Tom Gries created a series featuring another gang of rats: The Rat Patrol (1966).
The title is based on the old saying that promoted good health: An apple a day keeps the doctor away. This phrase originated in England and Wales in the 19th century.