This was only one of two appearances that Madge Blake made as Aunt Harriet Cooper during this season. She had all but retired due to illness.
This was Frank Gorshin's final appearance as the Riddler. In his final scene he promises to 'return like a boomerang' and indeed Gorshin's Riddler faced West & Ward as Batman & Robin once more in The Challenge (1979).
Marks James Brolin's 3rd appearance on the show. Previously played Reggie in The Catwoman Goeth (1966) and the armored car driver in The Cat and the Fiddle (1966)
Frank Gorshin's first appearance as The Riddler since the Batman movie, released a little over a year before. Gorshin had sat out the show's entire second season over contract disputes.
Beginning with this episode, sound effects were added to Batgirl's appearances in the opening credits.