Restaurant hour-long drama **Tattingers ** morphed into half-hour sitcom Nick and Hillary.
Hour-long scream fest of righteousness **The Practice ** spun into hour-long Shatner and Spader chewing goof-fest **Boston Legal ** designed to give David Kelley free therapy. I’d definitely say the shows are different genres - straight drama to comedy-drama (emphasis on the comedy).
Hour-long **Hercules: The Legendary Journeys ** spawned children’s show Young Hercules
Love, American Style --> Happy Days.
Tracey Ullman Show --> Simpsons
I wonder if cartoon spin-offs count?