In the latest issue of Doctor Who magazine, the exciting additions were named - and include Dara Lall, who will play Fudge in the first special, The Star Beast.
If you think that Fudge sounds familiar, that's because they are - the character actually first appeared in the original 1980 comic strip in Doctor Who Weekly.
Speaking about the character, executive producer Phil Collinson said: "Readers of last month’s DWM will have seen the creators of the Meep, Pat Mills and Dave Gibbons, delighted to discover that the character of Fudge has survived from page to screen.
"And it’s lovely to welcome Dara on board, as a character with such a fine and historic background."
As for the other three cast members, they are set to appear in the final 60th anniversary special, The Giggle. They include John MacKay, who will play television pioneer John Logie Baird.
Speaking to Doctor Who Magazine, returning showrunner Russell T Davies said of MacKay's addition: "John MacKay is the most perfect choice to play John Logie Baird – so perfect, I’ve done it twice!
"John first took on this role in my ITV production of Nolly, because Noele Gordon (played by Helena Bonham Carter) was, true fact fans, the first woman in the world to appear on colour TV, put there by JLB himself.
"So now, to have the same actor play the same character means that all my shows are set in the same universe, officially! But never mind me, John is a wonderful actor, and a perfect piece of casting by Andy Pryor and his team."
Former Coronation Street actor Charlie De Melo has also joined The Giggle cast as Charles Banerjee, with the actor being known to many soap fans as Imran Habeeb in Corrie from 2017 to 2022.
Collinson said of De Melo's role: "It’s such a delight to welcome Charlie on board. I was the producer of Coronation Street many years ago, and I’ve kept an eye on it ever since – that’s how we spotted Millie Gibson!
"So, when Charlie left the show, he was immediately on my radar, and we swooped in to get him into the show.
"You might have already glimpsed him in the trailer, and I can certainly say that Charles Banerjee is heading towards terrors we’ve never seen on screen before."
- Ncuti Gatwa 'blew everyone away' filming "pivotal" Doctor Who scene
- Paul McGann 'to return as Eighth Doctor in new Doctor Who spin-off'
Finally, Alexander Devrient will play Colonel Ibrahim, with Collinson also saying: "Long-term fans have grown up with the notion of the UNIT family, a regular cast of characters who appear alongside the Doctor every time he needs the services of the Unified Intelligence Taskforce.
More like this
"And it’s a great pleasure to welcome Alexander into the clan, as Colonel Christopher Ibrahim – he isn’t even given that first name until next year’s new season!
"Ibrahim is a UNIT stalwart, serving loyally alongside Kate Lethbridge-Stewart. But even he’s barely prepared for the dangers to come. It’s good to make Alexander part of the family. Let’s hope Colonel Ibrahim survives!"
The excitement continues to build for the 60th anniversary specials, which will begin airing with The Star Beast on Saturday 25th November 2023, with the subsequent two episodes airing each Saturday afterwards.
Of course, the new additions round out a cast helmed by returning David Tennant and Catherine Tate, with Tennant portraying the Fourteenth Doctor and not the Tenth.
It's a Sin star Neil Patrick Harris will play a nefarious antagonistic in the specials, now confirmed as The Toymaker, while Years and Years's Ruth Madeley, Heartstopper actress Yasmin Finney and Miriam Margolyes will also be featuring in the new specials.
Try Radio Times magazine today and get 10 issues for only £10 – subscribe now and celebrate the 60th anniversary of Doctor Who with a special issue of Radio Times. For more from the biggest stars in TV, listen to The Radio Times Podcast.