Big-Lipped Alligator Moment: Only in the Broadcast version: the Fourth Doctor and Romana being returned to their timeline results in the Doctor inexplicably lying in some grass in an alley and wearing his coat and scarf, and Romana standing in the doorway of the TARDIS telling him to hurry, due to having to rely on Stock Footage from the unfinished Shada.
Broken Base: Mainly how people view the Special Edition version of the programme. It's either a good attempt at a extended version of the programme, or a bad edit that felt too padded and the effects aren't as good as in the original release.
Ensemble Dark Horse: The Raston Warrior Robot. It only appeared in one scene, but that scene in question saw it take out a squadron of Cybermen.
Epileptic Trees: Where exactly the story takes place in the lives of the first three Doctors is a commonly-debated topic. The prevailing theories are that the First Doctor is taken during the events of "The War Machines" (as per this episode's novelization, which states that he's near his regeneration and on contemporary Earth, although one short story places it immediately after "The Daleks' Master Plan" and some have theorised that the First Doctor's bizarre absence and behaviour in "The Massacre" is due to being scooped into this adventure), the Second Doctor from some time during the theorized "Season 6B" (since he knows that Jamie and Zoe's memories of him were mostly erased, which happened minutes before he was forcibly regenerated), and the Third Doctor some point between "Death to the Daleks" and "Planet of the Spiders" (as he knows who Sarah Jane is, and there's no logical place to fit his appearance in prior to "Death to the Daleks").
Harsher in Hindsight: In this story, it's implied that Rassilon set up his game and the supposed prize of immortality as a trap to protect Gallifrey from any tyrants who might have ideas about taking over the planet. However, with every subsequent appearance by Rassilon depicting him as a Bad Boss or outright Omnicidal Maniac, together with his eventual return in the relaunch series, it instead ends up implying that the actual purpose of the Game of Rassilon is to eliminate any would-be tyrants... so that they won't get in the way in case Rassilon himself decides to come back and take over Gallifrey.
Hilarious in Hindsight: In an outtake, Jon Pertwee remarks "Well, that's the end of the Master" after Nicholas Courtney (in character as the Brigadier) knocks Anthony Ainley (in character as the Master) to the ground. Richard Hurndall then jokingly suggests that Courtney "kick him in the cobblers next time." "The Mark of the Rani" would see the titular villain knee the Master in the groin.
Ho Yay: The Master openly states that "a cosmos without the Doctor scarcely bears thinking about", further supporting the idea that he never truly intends to kill the Doctor. He's genuinely nice to the Doctor throughout the entire episode, though the Doctor sadly doesn't believe him, and is very miffed when One doesn't recognise him from their Academy days (what with him having a new, stolen body).
Memetic Mutation: No, not the mind probe!Explanation A line from Castellan that quickly gained infamy for how silly its delivery is, sounding like the actor attempted to enunciate every word in a different way. Since then, it's become common to quote among Classic Series fans as the archetypal example of bad line delivery in Doctor Who.
Narm: Sarah Jane gets injured falling off the lowest slope imaginable. Makes it more over the top in the syndicated version where that ended up being the cliffhanger for part 1.
Parody Displacement: The infamous "no, not the mind probe!" line was originally intended as a riff on a similar bit from "Frontier in Space" that Terrance Dicks found silly, to the extent where he planned for Castellan to deliver it in an intentionally campy manner. However, the actual on-screen delivery ended up surpassing the original in recognition via its stiff, overenunciated style, leading many fans to mistakenly see it as narm (when it wasn't meant to be serious to begin with).
The Fifth Doctor and Susan are also widely noted to have looked like they were checking each other out in their scenes together. Possibly a bit hard to play a convincing grandfather-granddaughter relationship with a ten-year age difference in the wrong direction.
There's a whole scene where the First Doctor appears to be checking out his granddaughter's arse that was so gobsmackingly overt that reruns cut it out.
Special Effect Failure: The Special Edition Time Scoop. The special edition editors thought CGI spirals would be more ominous than the black triangles used in the original. They were wrong.
The laser effects as the Master encounters the Third Doctor and later on the chess board are clearly just static digital lines drawn on top of the picture in the Broadcast version.
The diagram of the Tower on the brand new TARDIS console's monitors is clearly being generated by a BBC Micro.
The distortion effect representing the Fourth Doctor trapped in the Vortex is changed from the simple-but-effective digital wobbliness from Broadcast, to a strange "jigsaw puzzle" effect in the Special Edition.
The choice of photo has also changed, from a close-up of the Doctor and Romana in the barely visible study, to an overhead shot of the Doctor in the boat, making it much more obvious that it's a screen-grab from Shada.
The Raston Warrior Robot is very obviously just a person in full-body spandex, and its teleportation is equally obviously just footage jump-cutting to it being in a different place. RiffTrax hung a lampshade on the former in their live riffing of this episode, responding to the description of it as the most dangerous killing machine in the universe with "Where? Behind that spandex dork?"
The Fourth Doctor being restored to his proper timeline in the Broadcast version is taken from much later in "Shada" than the scene where he was taken, resulting in the Doctor inexplicably lying on the ground in an alley before darting urgently into the TARDIS at Romana's call.note The Special Edition replaces it with a long shot from the punting scene and the Time Scoop overlayed on top to imply he's been put back exactly where he was.
As well as the Special Edition photo choice mentioned above, the image used to represent the Fourth Doctor trapped is from a scene where he wears his coat and scarf, which he hadn't been wearing in the punting scene immediately before it.
Only the Second and Third Doctors see images of former companions (Jamie and Zoe for the former and Liz and Yates respectively). It would have been great to have the First Doctor and Susan see Ian and Barbara again, even if they are hallucinations, or even see Five have to confront the death of Adric once again (as the one time a hallucination of him did appear, the Fifth Doctor wasn't around to see it).
Some of the ways in which the story pairs off characters or actors misses great opportunities. Patrick Troughton and Nicholas Courtney are paired off for most of the story despite only sharing three stories together (though it works because the two find a good dynamic), but the reunion of Courtney and Jon Pertwee, who worked together for five whole seasons, is just two lines. And pairing Tegan off with the equally strong-willed First Doctor ought to be a great dynamic, but instead Tegan is left to silently follow him around looking sullen.
The Doctor and Susan being reunited would have been a great story on its own. Thankfully, the expanded universe took note.
The current Doctor having a brief reunion with Sarah Jane is also not played for any meaningfulness (especially since she appears to not even recognize him). Luckily, they would later have a proper emotional moment meeting each other again in the new series episode "School Reunion".
