Roseanne famously recast Lecy Goranson as Becky Conner after season 5, briefly replacing her with Sarah Chalke and many viewers still wonder why did Becky leave Roseanne in the first place, especially since Goranson later returned. When Becky’s Roseanne recast happened, TV recastings even on major shows weren’t rare. One of the most famous examples is the recasting of husband Darrin Stephens in the 1960s sitcom Bewitched, with actor Dick Sargent replacing original cast member Dick York, who was in failing health at the time.
https://screenrant.com/roseanne-becky-conner-recast-sarah-chalke-lecy-goranson-why/