Batman (1966) - Season 02

Despite being the most prominent villain during Season 1, Frank Gorshin was completely absent as The Riddler during Season 2, as Gorshin was holding out for a salary increase for continuing on in the role, which the studio refused to comply with. As a result, a storyline in Season 2 that was originally intended for the Riddler was instead given to a character called The Puzzler, while another storyline later on in Season 2 saw John Astin replace Gorshin in the role of the Riddler.