SEASON PREMIERE: This is Season 12 for this very long-running, still very funny sitcom – and it’s been announced that it’s coming to an end of its own volition, so savor them even more than usual. What I like most about this series is how organically and charmingly its characters have evolved, especially the peripheral characters who, over the years, have become more and more central. And following at 8:30 p.m. ET is the much younger, still sweet Young Sheldon.