The penultimate episode of Doctor Who: Flux saw the return of two fan favourites, and viewers didn't shy away from sharing their excitement.

'Flux: Survivors of the Flux' aired tonight (November 28), seeing the Doctor, Yaz and Dan face more peril in their quest to survive.

Jodie Whittaker's final season has brought back a number of characters and motifs from previous seasons and storylines, but tonight, two big returns particularly excited viewers.

jodie whittaker, doctor who season 13, episode 3
Ben Blackall//BBC

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The first was the return of the Ood, otherwise known as Oodkind, the tentacled humanoid species easily corrupted by evil forces.

First created by Russell T. Davies back in the show's second season, their return got a big reaction from fans.

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doctor who flux jodie whittaker episode 5
BBC

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The other big comeback this episode was UNIT, (Unified Intelligence Taskforce) the military organisation that investigates paranormal threats to the Earth.

Having first appeared in the 1960s, the organisation was initially called the United Nations Intelligence Taskforce, but had to change the name when the actual UN no longer wished to be associated.

doctor who flux jodie whittaker episode 5
BBC

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The story took viewers to the UNIT offices in 1967, revealing that's where the TARDIS is.

Here were some of the fan reactions...

doctor who flux jodie whittaker episode 5
BBC

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However, not all of the reactions to the latest episode were positive. Many fans and viewers took to Twitter to complain that this season has been too confusing, and difficult to follow.

Some attributed this to attempting to bring back too many elements from previous series, others blamed showrunner Chris Chibnall, and yet more said too many big guest stars had been shoehorned into this series.

doctor who flux jodie whittaker episode 5
BBC

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This seems to echo the viewing figures from the past five weeks, which have shown fewer and fewer fans have tuned in to each episode.

Although it only accounts for the live views (not those who watch it on catch-up later), the premiere drew a whopping 4.43 million viewers, which dropped to 3.45 in episode four.

It remains to be seen whether this downward trend will continue, or whether next week's finale will boost figures again.

Doctor Who: Flux (aka series 13) airs weekly every Sunday night on BBC One in the UK. In the US, the show airs on BBC America, with series 1-12 available on HBO Max.

For more information on Doctor Who: Time Fracture, head this way – tickets are also available via retailers including LOVEtheatre, London Theatre Direct, Fever and Ticketmaster.