"The Twin Dilemma" (season 21, episodes 23-26; originally aired 3/22/1984-3/30/1984)
Every regeneration story in Doctor Who is, in a sense, a twin dilemma: Who's the new guy, and how will he pick up the torch? They carry the double burden of (re-)introducing the much-changed star to potentially skeptical fans, and getting him out interacting with the universe where he can play the hero. "The Twin Dilemma," which introduces Colin Baker as the mercurial Sixth Doctor, is legendary for its excruciating failure on both those counts, routinely ranked dead last in fan polls and widely considered the start of the careening path to cancellation a few years later. Part of its bad rep was just bad timing: It had the ill luck to follow directly after "The Caves of Androzani," Peter Davison's final and most well-received story. But there's not much else that can take the sting out of this one: "Twin Dilemma" is just an unpleasant, tacky, dull affair starring an obnoxious, overbearing bully. The best that can be said for it is that the idea behind the Sixth Doctor's unlikeable character wasn't terrible; but the actual presentation was not just terrible, but toxic.
The story kicks off immediately after the events of "Androzani," when Davison's Fifth Doctor nobly gave his companion Peri their only dose of antidote to the poison that was killing them both, collapsed, and regenerated. It was one of his character's finest moments, a selfless sacrifice that saved not a galaxy or a planet, but just one other person—without making too much out of it, it was a reminder that good deeds don't mean less just because they're on a smaller scale. That kindness was the Davison Doctor's most appealing quality, and losing that with Six was meant to be a huge shock.
Appropriately, there's a double meaning in the title of "The Twin Dilemma." Of course, there's Romulus and Remus, the bowl-cutted boy geniuses whose kidnapping kicks off the main story. But the new Doctor goes through a twin dilemma of his own, as his unstable regeneration leaves him in a sort of bipolar state, at the mercy of violent mood swings that yaw him from cringing fear to homicidal paranoia. Going for maximum shock value, the show even makes the Doctor so wildly unhinged that he tries to strangle Peri because her name is coincidentally the same as a mythological Persian evil spirit. Soon after, calmer but still emotionally unstable, and without actually apologizing for his attempted murder, he decides to atone for his crime as a hermit on some desolate asteroid, dragging Peri along as his servant. He's unremittingly arrogant, mean-spirited and verbally abusive, and has also developed the worst fashion sense in all of time and space. (Baker had suggested a black-velvet suit to match his character's overt dark side, but was overruled by producer John Nathan-Turner, who dressed him instead in what Baker later described as an "explosion in a rainbow factory.")
It's a bold move to deliberately make your main character unlikeable, but there was a purpose to it. Whether it was a worthwhile purpose is another matter, but there was a purpose. As we've seen from previous regeneration stories, the introduction of a new Doctor was also a chance to refresh the entire series, and the new persona of the central character was usually a deliberate contrast to the one before. For three years, Peter Davison had played the Doctor as a quiet, diplomatic hero—with his cream-colored cricket outfit and blond hair, he was almost literally a white knight. An antiheroic Doctor was by no means a bad idea, and had been part of the mosaic of the Doctor's personality since the start of the show. Tom Baker could be arrogant, Jon Pertwee's courtliness was interwoven with flashes of haughtiness, and William Hartnell had been snappish, paranoid and malevolent in "An Unearthly Child." But for the Sixth Doctor, the show's creative staff, led by Nathan-Turner and script editor Eric Saward, took a wild gamble and ratcheted up the Doctor's worst characteristics to extremes. Previous incarnations had their heroism leavened by streaks of vanity, self-importance, pompousness, and arrogance, but in the Sixth Doctor, those became his most prominent qualities. There's more than a little cowardice in Six here as well, which also connects to his earliest roots—the Hartnell Doctor was a runaway in fear of his own people, after all. (And even the murderous psychotic break isn't totally without precedent—remember when Hartnell nearly clubbed a caveman to death with a rock?) A bad-egg Doctor is a potentially interesting twist—the idea was that Six would, over time, grow out of that obnoxiousness and rediscover his best self.
But "Twin Dilemma" doesn't present that idea with any real nuance or sensitivity. Instead, he's an extreme Doctor, in the way that Rob Liefeld comics, Poochie from the Simpsons, and Mountain Dew Code Red are extreme: A crude version of the good stuff that equates being louder with being more awesome.
The story goes that Nathan-Turner hired Baker—no relation to Fourth Doctor Tom Baker—largely because he was impressed by Baker's jokes at a wedding they both attended. That's been used as a knock against Baker, but it's not really fair. Baker had a bushelful of TV work on his resume before becoming the new Time Lord, including a small role as Commander Maxil in the Davison episode "Arc of Infinity" and a prominent role as a recurring villain on a 1970s drama called The Brothers. He was enthusiastic about being the new Doctor and stated publicly that he hoped to beat Tom Baker's seven-year record in the role. And while he wasn't in the other Baker's charismatic league, he was an otherwise solid actor dealt a bad hand in terms of what he was required to do. Although "Twin Dilemma" catches him in some wild overacting, he was, after all, being asked to play crazy. It wasn't really his fault.
The Doctor spends the first couple of episodes wearing out his welcome with the audience by belittling, bullying, and terrorizing the understandably disconsolate Peri. Eventually, the two of them leave the TARDIS and stumble into the main plot on the asteroid Titan 3, teaming up with space cop Hugo Lang in search of two kidnapped identical twins, Romulus and Remus. They're mathematical geniuses who have the ability to, we're told, "alter reality on a massive scale" with their calculations. We're told this, but we don't really see it: In practice, it looks like they're just playing video games. The twins have been taken by Azmael, an old Time Lord friend of the Doctor's who is now working for Mestor, a superintelligent giant slug that rules the planet Jaconda with an iron slime-tendril.
The Doctor's technicolor-vomit clown costume was no accident, but was John Nathan-Turner's idea of how to best visually reflect the character's inner chaos. In practice, it just made him look foolish, and made it that much harder for the show to pull off the kind of grim and violent stories that it would repeatedly attempt in Season 22. It was ugly on its own terms, but also had a domino effect on the rest of the program. In order to visually compete with That Suit, the sets and the other costumes began to become more colorful and more garish in their own right—like Hugo Lang's tinfoil jacket, or the space police's gigantic star badges that look like they belong on top of Christmas trees. Perhaps Nathan-Turner thought the suit would gloss over the Doctor's bad temper—he apparently was inspired by his own love of Hawaiian shirts, and once said that “I always felt that people … assumed you were a warm, friendly, funny, likeable, approachable sort of person if you were wearing a Hawaiian shirt."