John Astin gave up top billing to Carolyn Jones
https://www.metv.com/stories/john-astin-fought-the-good-fight-to-keep-gomez-from-being-bald
John Astin was signed to the TV show first, and his contract gave him top billing. The article explains that they could not find an actress to fit their vision for Morticia, until they got Carolyn Jones. She wanted top billing and Astin thought she was perfect for the part. He said that he gladly lined out the top billing provision in his contract, giving it to her.