It’s still not too late for Clarissa Now .
Mystik Spiral
Spin-off of: Daria
Plot: Trent Lane and his band, Mystik Spiral, move into a rundown house in the "cool town" Mirage, where they hope to make it big.
Why it never happened: In 2001, following the making of the final Daria movie “Is It College Yet?,” MTV Animation abruptly shutdown and consequently the show.
The Mertzes
Spin-off of: I Love Lucy
Plot: Not too much is known about the plot, other than it would be the story of Fred and Ethel Mertz post I Love Lucy.
Why it never happened: According to Rob Edelman and Audrey Kupferberg’s book Meet the Mertzes: The Life Stories of I Love Lucy's Other Couple; Vivian Vance (Ethel) and William Frawley (Fred) had a deep hate towards each other.
When Vivian found out about the proposed spin-off she nixed the idea, she could not stomach the idea of working with William again. She refused to film the pilot and a $50,000 bonus Desi Arnaz offered her.
Jackée
Spin-off of: 227
Plot: Sandra Clark (portrayed by Jackée Harry) moves to New York City to start a career in the film industry.
Why it never happened: The spin-off ran as an episode 227, during its fourth season. However, NBC decided against picking up the series and Sandra was sent back to Washington, D.C.
The Art of Being Nick
Spin-off of: Family Ties
Plot: Nick Moore (portrayed by Scott Valentine), who was Mallory's boyfriend on Family Ties, moves to New York City to live with his sister and nephew. Notably, the series also costarred a young Julia Louis-Dreyfus.
Why it never happened: This was the third attempt by producers to spin-off the character and the pilot did do well in the ratings; but reportedly NBC did want to not pick-up the series because they were reluctant to lose the popular Nick character on Family Ties.
Via: ioffer.com