Young Sheldon

CBS | 8:00 pm

This prequel to "The Big Bang Theory" closes its fourth season with a finale called "The Wild and Woolly World of Nonlinear Dynamics," in which young Missy's (Raegan Revord) first heartbreak sparks a series of events affecting brother Sheldon (Iain Armitage) and the entire Cooper household. Fans can rest easy on one point, though: There's no real-world heartache for this show's cast and creative team, since CBS recently renewed "Young Sheldon" for three more seasons.