Spin-offs are a tricky beast. Nail it and you get a Frasier. Go about it all wrong and you've got a Joey on your hands.
So it's perhaps no surprise that for every spin-off that makes it to our screens, there are dozens of ideas that don't. Some of this lot even made it as far as shooting a pilot, before being cast aside by the telly gods.
1. Prison Break: Cherry Hill
Plans were once afoot to make Prison Break a CSI-style franchise, with spin-off Cherry Hill following well-to-do housewife Molly as she's thrown behind bars in a women's prison.
Molly was going to be introduced in the parent show's third season, until the 2007-08 Writers Guild of America strike forced Prison Break to shut down production and rejig storylines, nixing the Molly character and thus her series.
2. Supernatural: Bloodlines
Lucien Laviscount played Ennis Ross, rookie hunter of all things paranormal, in the 2014 Supernatural episode 'Bloodlines' – with the intention that he'd go on to lead his own series.
The new show would have chronicled the war between hunters and monsters in Chicago. The CW passed on the project, while remaining open to the possibility of launching a different spin-off from their longest-running series.
3. Assignment: Earth
Another planted spin-off – or what's known in the business as a 'backdoor pilot' – was Assignment: Earth, a potential sister series to the original Star Trek. The final episode of Trek's second season introduced Gary Seven (Robert Lansing), an alien from the 24th century sent back in time to protect Earth's history from outside interference.
Gene Roddenberry had hoped to devise more standalone adventures for Gary and his team, human assistant Roberta Lincoln (Teri Garr) and... erm... a cat named Isis – but the spin-off never (*cough*) materialised.
4. The Farm
Easily the worst episode that NBC's The Office ever produced, it's easy to see why this backdoor pilot about Dwight (Rainn Wilson) and his family running Schrute Farms failed to spawn a full series.
Instead, the original show wrapped things up neatly with a terrific, touching final episode – no spin-off required, thank you very much.
5. Marvel's Most Wanted
ABC originally began plotting a spin-off from Agents of SHIELD starring Adrianne Palicki and Nick Blood as super-spy lovers Bobbi Morse and Lance Hunter back in early 2015.
The idea was dropped, only to resurface a second time last year with Palicki and Blood being written out of the parent show to shoot a pilot for Most Wanted. ABC eventually passed for a second time, leaving the pair without any show at all. Harsh.
6. How I Met Your Dad
There's another How I Met Your Mother spin-off in the works at the moment, but the first attempt at following up the hit sitcom with the super-divisive ending came in 2014.
Essentially a gender-swapped remake of the original, the How I Met Your Dad pilot starred Greta 'way too good for this' Gerwig as its lead, with Meg Ryan providing a voiceover as the older version of her character Sally.
CBS passed, but the revamped version – more formally titled How I Met Your Father – is still in the running for a series pick-up.
7. Springfield
Remember that brilliant Simpsons outing '22 Short Films About Springfield'? The one with Steamed Hams, the giant man in his tiny car and Chief Wiggum doing Pulp Fiction?
The success of the episode, which focused on Springfield's other residents outside of the Simpson clan, almost led to a spin-off, as former showrunner Josh Weinstein told Digital Spy.
"We felt at that time – around season seven – that we all knew the family so well, so let's start exploring all these great side-characters," he explained.
"It would be a chance to tell full stories about these other characters, but that never happened. I think it could've been great, but everyone was so busy at the time."
