In television, it seems like there's never too much of a good thing. If you have a popular series or popular character, spread the joy around. A spin-off is a fresh show based on characters or situations from an established series. One approach is to put a supporting character into a new situation. For instance, Angel, the vampire-with-a-soul who battled evil alongside "Buffy the Vampire Slayer," took his crusade to Los Angeles. In another tactic, the new pilot is introduced as an episode on a well-known sitcom. That's how the space alien Mork ("Mork & Mindy") came to earth; he showed up on "Happy Days."
Sometimes spin-offs are less than successful. "The Brady Brides," an offshoot of "The Brady Bunch," centered on sisters Marcia and Jan when they married and shared a house. The audience wasn't impressed, and the show was history after 10 episodes. Spin-offs can make it big, however, and some even overshadow the original show. The nerve!