Where a show as popular as Doctor Who is concerned, spin-offs were always going to be inevitable. Over the years, the sci-fi series has introduced several various shows that tie in to its unique mythology. Some admittedly were received less enthusiastically than others but in Torchwood's case, it's fair to say that it was a qualified success.
Torchwood was unique in the world of Doctor Who, as it was the first series to be specifically catered towards an adult audience. As a result, while it did keep to the general rules of the Whoniverse, Torchwood did differ occasionally from its parent program.
10 Same Actor, Different Characters
Almost every show on television is guilty of casting the same actor in dual roles at least once and Torchwood was no exception. In Season 1 of Doctor Who, Eve Myles played a young maid called Gwyneth, who helped to banish the Gelth from this world.
When Torchwood was commissioned, Myles was cast again, this time as Gwen Cooper, who was the show's primary female lead. Considering that Doctor Who's original showrunners had created the concept of regeneration, this peculiar piece of casting was also explained away in the Season 4 finale of Doctor Who. However, it was still worth noting so it makes this list.
9 Curse Words And Bloody Violence
Until Torchwood came along, the Doctor Who universe was very tame and kid-friendly. When viewers first got a glimpse of Captain Jack's new show, though, they were inundated with swear words and grotesque violence.
While Torchwood was very definitely a program for adults only, its first season could have benefited greatly from being toned down slightly. Fortunately, the showrunners rectified this mistake in the show's second season, which was much better received by viewers and critics alike. The mature content was still present, but it felt more natural and refined.
8 The Rift's Untapped Potential
Torchwood's main plot device for the first two seasons was the Rift, a fissure in time and Space first established in Doctor Who. Its purpose was to act as a basic portal through which aliens could arrive in Cardiff. However, the Doctor also used the rift as an energy source for the TARDIS.
While this was done after Torchwood's first season had aired, there was plenty of opportunity in the second season to set up the Rift as a source of power. Ultimately though, this storyline was left unused. which seemed odd considering it had massive potential.
7 The Doctor's Absence
The Doctor is a shapeshifting, time-travelling alien from the planet Gallifrey, so naturally he can't be expected to spend all of his time protecting our world, especially considering that he is needed by so many others. However, given that Torchwood and Doctor Who share the same universe, the Doctor has been pretty noticeably absent on more than one occasion.
How about the time when the devil Abaddon invaded the streets of Wales? Or when every single child on Earth stopped at the same time? Or when human beings suddenly became immortal? All of these situations could have benefited from some extra help from a benevolent alien.
6 A Lack Of Crossovers
This is similar to the previous entry, but it encompasses the whole of Doctor Who, rather than just the titular Time Lord. Aside from a brief but welcome appearance from Martha Jones in Season 2, Torchwood had always been fairly isolated from the rest of the Doctor Who community.
While other spin-offs had featured appearances from the Doctor himself — and even companions from the old series, thanks to The Sarah Jane Adventures — Torchwood was severely lacking on that front. A couple of characters had appeared on Doctor Who, but never the other way around.
5 Doctor Who's Own Version Of Torchwood
The organization that eventually became Torchwood actually first appeared in Doctor Who as the long-running arc in its second season. This version of Torchwood was far more mainstream and was situated in Canary Wharf, a far cry from a damp basement in Cardiff.
The question is, where did all the government funding go? When Doctor Who's Torchwood (Torchwood One) fell, Torchwood Cardiff had to step up as the head of the organization. Surely this should have warranted a makeover, or at least more resources, rather than just five or six team members at a time?
4 Jack's Vortex Manipulator
Much like Torchwood itself, the vortex manipulator also made its debut on Doctor Who. However, when it was first introduced, it was nothing more than a cheap time-travel device — and quite uncomfortable as well.
When it popped up again on Jack's wrist in Torchwood, its function had changed drastically. It could no longer travel through time but at least we got an in-house explanation for the malfunction. What the show didn't explain, though, was how it suddenly became a multi-functional device, arguably even more useful than the Doctor's own sonic screwdriver.
3 The Government's Influence Over Jack Harkness
Torchwood was established as an organization outside the government, founded by Queen Victoria to protect Earth from supernatural threats, including the Doctor himself. When the show first began back in 2006, Jack Harkness, a fan favorite companion to the Ninth Doctor, was discovered to be its leader.
This lined up perfectly with what the audience already knew about Jack; he was charismatic and charming with a natural leadership ability. What was less convincing, however, was that Jack would let himself work for, or at least with, an institution. The government didn't run Torchwood, but they knew enough about it to attempt to destroy it.
2 Jack's Past As A Con Artist
When Jack first appeared in Doctor Who, he seemed to be the perfect man to run away with. He was funny, sexy and charming. However, it was soon discovered that he was in fact a con man just trying to make a quick intergalactic buck. Before the big reveal, though, he told the Doctor and Rose that he used to be a Time Agent.
While the concept of the Time Agency was brought up frequently in Torchwood, no mention was ever made about Jack's past as a con man. Again, this felt like it had potential as an interesting storyline, or at least as a decent episode, but for whatever reason, Torchwood decided to retcon Jack's history.
1 Peter Capaldi As John Frobisher
The third season of Torchwood is widely regarded as its best, due to phenomenal storytelling and amazing guest stars. One of these such actors was Peter Capaldi who played John Frobisher, a low-level government official tasked with overseeing the demands of the 456.
However, fans may be more familiar with Capaldi in his more prominent role as the 12th Doctor himself. Capaldi had previously played Caecilius in Doctor Who and that character's similarity to the Doctor was later explained in the series. In contrast, John Frobisher was forgotten and an explanation for he and the Doctor sharing the same likeness was never provided.