[[caption-width-right:350: Stand down! ''[[MundaneMadeAwesome I have a medallion!]]'']]
->''You're just an aging hippie, Professor.''

The Doctor and Ace get junk mail in the TARDIS and head off to a circus that has, inexplicably, set up shop on a desert planet. They poke around a bit -- buying gross food from a travelling vendor, chit-chatting with self-important adventurer Captain Cook and his punk companion Mags, trying to flag down a ride from a ''Film/MadMax'' extra -- and utterly fail to notice that this is the sort of circus that people run away ''from''.

In fact, the CircusOfFear has adopted the innovative cost-saving practice of imprisoning its customers and making ''them'' perform, with a penalty of death if the audience -- who consist solely of a jaded CreepyMonotone trio of mother, father, and little girl -- are bored. So it is that Ace and the Doctor promptly find themselves backstage, in an unusually well-secured green room together with Captain Cook, Mags, the BadassBiker guy, and a starstruck über-fan named [=WhizzKid=].

After much sneaking around in the circus's billowing tent backstage, the Doctor and Ace discover that it was once a free-spirited hippie circus of, like, ''love'' and ''joy'' and ''freedom'', man... until they settled down on this planet, where they apparently all had to sign their circus over to evil gods. Guess they should have read the HOA fine print.

Eventually, Ace and Mags (who turns out to be a werewolf) go to dig a [[HumongousMecha medium-sized mecha]] out of the desert, which they use to fend off the extremely creepy head clown. Now they just need to find and destroy the evil amulet controlling the circus, while the Doctor is left to amuse the Evil Gods of Ragnarok (the true form of the creepy audience family). He does so by improvising egg tricks, rope tricks, juggling tricks, fire tricks, snake tricks, sword tricks and upside-down escapism tricks, and looks like he could have merrily gone on for a few more hours and is having rather a lot more fun than the Gods themselves. Eventually, though, Ace tosses him the evil amulet through a dimensional portal.

The amulet gets destroyed, which takes out the circus in a giant fireball of evil gods and creepy clowns, and Sylvester [=McCoy=] [[UnflinchingWalk walks unflinchingly]] -- both in-character and in real life, and just a little bit on fire because the BBC pyrotechnics crew screwed up. [[note]]They planned to do the explosion with an air blast, but brought the wrong equipment and ended up having to do it with real pyrotechnics. There are conflicting reports as to whether [=McCoy=] was told about this.[[/note]]

* AlienLunch: Ace and the Doctor try to make friends with a stallholder by buying a fruit from her. Then they have to eat it, and pretend that they like it.
* {{Animorphism}}
* AssholeVictim: Does anyone really mourn for [[JerkAss Captain Cook]] after Werewolf!Mags mauls him?
* BadassBiker: Nord, Vandal Of The Road.
* BerserkButton: Captain Cook doesn't mind being called a scoundrel or a meddling fool, but "[[ITakeOffenseToThatLastOne crushing bore]]" cuts him to the quick.
* BigBad: The Gods of Ragnarok.
* BondOneLiner: The Doctor gets a couple.
** After disabling a homicidal robot bus-conductor with his own ticket machine: "Just the ticket."
** After knocking out a homicidal robot clown with a juggling club: "Join the club."
* TheCastShowoff: Creator/SylvesterMcCoy starts the episode by juggling and playing the spoons, and goes on to show every single magic trick he can think of.
* CircusOfFear: It's surprising that it took ''Doctor Who'' twenty-five years to do this.
* ContinuityNod: While Ace's looking for her rucksack in the TARDIS wardrobe, she throws the Fifth Doctor's coat to the floor and emerges a while later, wearing the Fourth Doctor's scarf. Mel's blue-and-white polka dot blouse from "[[{{Recap/DoctorWhoS24E2ParadiseTowers}} Paradise Towers]]" is also visible.
** One so subtle people don't usually notice until it's pointed out: the Captain's double-headed coins appear to depict an [[{{Recap/DoctorWhoS9E2TheCurseOfPeladon}} Alpha]] [[{{Recap/DoctorWhoS11E4TheMonsterOfPeladon}} Centaurian]].
* CreatorCameo: The director, Alan Wareing, provides the divine voice for the "little girl" God. This was because, due to delays in the production, the production team had, by the time these scenes came to be recorded, exhausted the number of days that Kathryn Ludlow, the child actress who played the human form and voice of the "little girl" God, could commit to the serial under child labour laws.
* CreepyChild: The "little girl" god.
* CreepyCircusMusic: Used to great effect. It's just similar enough to some well-known circus tunes to be off-putting, seems to come from nowhere inside the circus tent, plays during [[SoundtrackDissonance some of the most surreal and creepy scenes in the story]], is used to drown out a young woman's screams, and is [[EarWorm just catchy enough to stay in your head]]...
* DaylightHorror: The circus tent is dimly lit, but the evil gods' native dimension is a sunlit arena.
* DidYouJustScamCthulhu: The Doctor versus the Gods of Ragnarok.
* TheDragon: The Chief Clown.
* DrivenToSuicide: Bellboy.
* EgomaniacHunter: Captain Cook.
* EldritchAbomination: The Gods of Ragnarok.
* EveryoneCallsHimBarkeep: If the Ringmaster and the Chief Clown ever had names, nobody uses them now.
* EvilCounterpart: The Captain and Mags are a dark mirror for the Doctor and Ace, if the Doctor were a self-serving, abusive coward.
* EvilIsNotAToy: Deadbeat (in his backstory) and Captain Cook both planned to make deals with the power behind the Circus. When Deadbeat tried he lost his mind; Cook became a revenant under their control before he got the chance to negotiate.
* EvilSoundsDeep: The Gods when they drop their facade, and the Chief Clown when he loses it.
* FanBoy / StrawFan: [=WhizzKid=] was, yes, a sly parody of ''Series/DoctorWho'' fans.
* {{Foil}}: Captain Cook and Mags serve as a parallel to the Doctor and Ace, with the difference being that Cook is a pompous coward who can't actually walk the walk the way the Doctor can.
* FourthWallObserver: Is there any other explanation for why the Chief Clown does his little flourish direct to camera when Bellboy kills himself, given that there are only robots present otherwise?
* GratuitousRap: The circus' MC is a rapper. Why? Because!
* HairTriggerTemper: Nord, Vandal of the Road
* HippieBus: There's a broken-down one in the desert near the Circus, a relic of its free-spirited hippie days.
* TheHyena: The Chief Clown. Goes with the general MonsterClown-ness.
* IKnowYoureInThereSomewhereFight: The Doctor to Mags. He's half-successful, as she kills Captain Cook, but spares the Doctor.
* ImmoralRealityShow: Visitors to the circus are killed for the amusement of the Gods of Ragnarok.
* ITakeOffenceToThatLastOne: See BerserkButton above.
* LovelyAssistant: When the Ringmaster tempts the Doctor into agreeing to perform, he attempts to pigeonhole Ace as the LovelyAssistant. Ace, already creeped out by the circus, prefers to run away as far and as fast as she can.
* TheMadHatter: Deadbeat/Kingpin
* MilesGloriosus: Captain Cook, a blustering braggart who is quick to pontificate about his many exploits, but [[DirtyCoward makes sure to keep himself as far from danger as he can]]. It's a minor moment of awesome when, even as Cook has him penned in by a werewolf and at the mercy of the clowns, the Doctor finally has all he can stomach of Cook's tedious waffling and tells him to shut up.
* MonsterClown: The Chief Clown
* NewAgeRetroHippie: Kingpin, Bellboy, Flower Child, ''et. al.'' Stephen Wyatt has said that the story was consciously intended to be partly about the failure of sixties hippie ideals in the seventies and eighties.
* NiceJobFixingItVillain: Ace and Kingpin would never have retrieved the other part of the amulet if the ticket collector robot hadn't accidentally broken its box open while trying to kill Ace.
* NoNameGiven: Most of the guest characters are identified only by job title ("Ringmaster", "Stallslady"), obvious nicknames ("Whizz Kid", "Flowerchild"), or in the case of the Ragnarok gods, family relationship.
* NobodyCallsMeChicken: Done by the spambot to Ace to provoke her into going to Segonax.
* NoShirtLongJacket: Bellboy.
* OurWerewolvesAreDifferent: Mags is an alien with no control over her transformations.
* PsychopathicManchild: The villains are {{Eldritch Abomination}}s who need to be constantly entertained.
* RevenantZombie: The Captain after the Gods raise him.
* ShoutOut: The Gods of [[NorseMythology Ragnarok]].
* SimilarSquad: Captain Cook and Mags, for the Doctor and Ace.
* SpotOfTea: Captain Cook is taking tea in every scene in which he appears. Even when the party is attacked by a HumongousMecha.
* StandardSnippet: The Ringmaster's entrance is accompanied by "Entry Of The Gladiators."
* StylisticSuck: The Ringmaster's raps, according to Wyatt on the DVD, are meant to be bad and indicate his diminishing artistic abilities. Although this may be an excuse.
* TakeThat:
** The whole serial is a massive Take That. All the performers at the Psychic Circus are paraded in front of [[Creator/MichaelGrade cold, unfeeling cosmic figures with a penchant for destroying anyone who fails to entertain them]]. The Doctor does simple tricks to bide for time, but once he gets a chance to destroy the Gods of Ragnarok, he takes a bow and casually strolls out of the exploding circus, showing up all the other performers and proving once again why he's a walking Crowning Moment of Awesome. It ain't called '''Greatest Show in the Galaxy''' for nothing. Sadly, the show's newfound confidence (and storytelling quality) would be cut short, as under a year later, it would be canceled until 2005.
** The Captain has been alleged to be based on the convention behaviour of certain well-known ''Doctor Who'' figures.
* TakeThatAudience: Whizz Kid is meant as a deeply unsubtle one to the more... obsessed fans of Doctor Who.
-->'''Whizz Kid:''' Well yes, of course. I've never been able to visit it before now, but I've got all sorts of souvenirs. Copies of all the advertising satellites that have ever been sent out. All the posters. I had a long correspondence with one of the founder members too, soon after it started. Although I never got to see the early days, I know it's not as good as it used to be but I'm still terribly interested.
** The Gods of Ragnarok can be read as this to the general audience at large. In the circus tent, they're presented as a rather dull family with no imagination of their own who just sit disinterestedly in front of a parade of entertainment moaning about how nothing's ever good enough to interest them no matter how creative it is, and anything they vote down is pretty much wiped out of existence.
* TarotTroubles: When Morgana offers to tell the Doctor his future she draws The Hanged Man card from her tarot deck. This serves as {{Foreshadowing}} to a later scene where The Doctor is hanged from a rope by his ankles while performing an escapology trick.
* TennisBoss: The Doctor defeats the Gods of Ragnarock by using the mirror amulet to reflect their energy blasts and collapse the roof of their balcony seat on them.
* ThemeTuneRap
* TwoHeadedCoin: Captain Cook uses a two-headed coin to win a coin toss against Nord and force the barbarian to enter the ring first. He later reveals that he has two-tailed coin as well, so Nord was screwed no matter what he called.
* UnflinchingWalk: Though if you look close, you can see that Creator/SylvesterMcCoy does indeed flinch slightly (because the explosion was bigger than he expected).
* VillainSong: Christopher Guard and Mark Ayres wrote a Villain Song, "We Are the Psychic Circus", for the Psychic Circus characters, which was rejected for release by the BBC but finally appeared on the DVD issue. It's [[DamnedByFaintPraise not as bad as "Doctor in Distress"]].
* AWildRapperAppears: "The Greatest Show in the Galaxy" opens with the Ringmaster unexpectedly rapping expository dialogue: a dramatic device not used before or since in the show's entire history.
* [[WolfMan Wolf Girl]]: As is common in ''Series/DoctorWho'' -- see, for instance, [[Recap/DoctorWhoS18E4StateOfDecay its]] [[Recap/DoctorWhoS26E3TheCurseOfFenric many]] [[Recap/DoctorWhoS31E6TheVampiresOfVenice vampires]] -- the specific variety of werewolf seen here has never been seen before and never will be again. Convergent evolution, we guess.
* WrenchWench: In Episode 1, Ace instantly diagnoses the problem with Nord's engine and offers to help him repair it -- to the point where she seems to be channelling [[Recap/DoctorWhoS24E3DeltaAndTheBannermen Ray]].
* YouHaveOutlivedYourUsefulness: The [[DroppedABridgeOnHim rather perfunctory]] killing of the Ringmaster and Morgana, after the Captain's death rouses the Gods' bloodlust with no further outsider victims available.