Although it was rumoured Kirk Cameron had Julie McCullough fired, the producers state McCullough left for storyline reasons. There was never any plans for Mike and Julie to get married because fans would not accept Mike Seaver as a married man.
Julie McCullough, who played Kirk Cameron's love interest Julie Costello during the fourth season, was abruptly fired from the show at the start of filming for the episode "Mike and Julie's Wedding" (in which her character would have married Mike Seaver). When she arrived for filming, she was given a new script, in which Julie left Mike at the altar. While no official reason was given to McCullough, it was common knowledge that Kirk Cameron had demanded that she be fired from the series. Cameron, who had become a born again Christian several years earlier, disliked McCullough because the actress had posed in Playboy months before being hired, and demanded her firing as a condition of his signing a new contract. This caused a huge backlash among fans of the series, forcing the show's producers to bring a reluctant McCullough (who had wanted nothing more to do with the show and Kirk Cameron) back in a hastily written episode to give the Julie character proper send-off.