For every successful spin-off - your Frasier, Angel or Melrose Place - there are many more that didn't quite make the grade. There's a difficult alchemy to spin-offs. If you prune off one single element of a show you can, with good writing, grow it into something brilliant in its own right, or it can just wither and die embarrassingly if the idea isn't sufficiently strong.
Here are a few TV off-shoots that did their best but could never match the successful shows that inspired them.
It was always going to be a very tough act to follow. Battlestar Galactica grew from an unfancied reboot of a cheesy old sci-fi about humans at war with robots and became one of the most celebrated series of the last decade. Its grand conclusion left audiences wanting more and the proposed spin-off was a smart idea. The premise was to go back to a time long before the events of Galactica to follow the two families who would become the most important players of the war. On one side was Joseph Adama, the father of the man who would lead the humans in the fight back against the vengeful machines, aka Cylons. On the other side was Daniel Graystone, the man who invented the Cylons in a misbegotten attempt to bring back his dead daughter. The themes of grief, class and destiny were all well handled, but with none of the firepower of Galactica it felt dry by comparison and audiences tailed off. It was cancelled before the end of its first season.
The Girl From U.N.C.L.E.
An attempt to recreate the spy thrills of The Man From U.N.C.L.E. with about 100% more sexism. Stefanie Powers played U.N.C.L.E. agent April Dancer, who tended to stop the world's bad guys not by killing them but by flirting them into submission. It was much sillier than its brother show and was quite quickly cancelled due to lack of interest. Notable for a crossover episode in which April and U.N.C.L.E.'s Napoleon Solo (Robert Vaughn) joined forces to battle Mother Muffin, a villainess played by Boris Karloff in drag.
The Golden Palace
The Golden Girls was such a massive success that after Bea Arthur left there was no desire to let the other three just go and enjoy their retirement. So they were all packed off to run a hotel in Miami. Obviously. Classic 90s TV lateral thinking. Nobody really liked three old ladies being put to work rather than mooching about being sassy and eating cheesecake and the show failed to make it to a second season.
People were lining up to kick this Friends spin-off before the sextet had even finished their last Central Perk coffee, but the resulting show had little in the way of defence. Joey went off to Hollywood to pursue his acting career and moved in with his sister (Drea de Matteo). The Joey of this show was nothing like the swaggering, loveable character from Friends. He was useless both professionally (not unknown for Joey) and romantically (unheard of for Joey). Friends worked because of the combination of six people, while Joey showed that you can't make a satisfying dish with just one of the necessary ingredients. Despite tumbling ratings it made it to a second season, which was cut short.
There's a whiff of marketing meeting around this one. It reeks of a need to make something 'hip' to appeal to 'the kidz'. The Looney Tunes characters are classics but this attempt to turn them into superheroes is just weird. Well, technically it's not the actual Looney Tunes characters themselves but future descendents of Bugs, Daffy and co (let's forget that this posits a world in which Bugs Bunny dies) who have been bestowed super powers after a meteor strikes Acmetropolis. Sometimes enjoyably odd, but also too far from the spirit of the cartoons that birthed it, it lasted two seasons. Notable for an interesting roster of guest voices, including Bootsy Collins, Tim Curry, Michael Clarke Duncan, The Big Bang Theory's Kaley Cuoco and...Serena Williams
Spooks: Code 9
Extremely cynical as spin-offs go. All this teen show has in common with the adult spy drama Spooks is the first part of its name. It's set in an entirely different world, in which London suffered a nuclear attack during the 2012 Olympic Games, turning it into a radioactive wasteland and driving MI5 to create groups across the UK to fend off further attack. There are no crossover characters or storylines. Few people were convinced by a reality in which the nation's security was put in the hands of a bunch of attractive people barely out of school and the lazy attempt to drum up an audience by grafting it to the Spooks brand was met with much hostility. It flopped and proved an expensive lesson to the BBC.
Joanie Loves Chachi
Scott Baio became a popular heartthrob, despite essentially being the Scrappy Doo of Happy Days, so he was a natural choice for a spin-off. The premise had young lovers Joanie and Chachi (Erin Moran and Baio) moving to Chicago to pursue their dreams of a music career. Audiences didn't share those dreams and the show only managed two short seasons. Joanie and Chachi then returned to Happy Days, smiling through their shattered dreams.
Images: AllStar, Rex Features