Jon Pertwee gave us the Doctor as action hero. In his previous incarnations, the Doctor took on his foes with intelligence and guile, strategizing from the sidelines and usually leaving the physical heroics to his younger male companions. But Pertwees Third Doctor, though no less brilliant or analytical than his predecessors, would often go toe-to-toe with his enemies, himself, as quick to throw a punch as offer a condescending put-down. Exiled to Earth, and employed by UNIT as their scientific advisor, the Doctor became an extra-terrestrial Sherlock Holmes-cum-James Bond-style crusader, defending the planet from a host of alien, as well as homegrown, threats. Pertwees era also brought color to Doctor Who, and marked its first significant step towards darker and more complex content. The prior seasons, for all their horror/sci-fi elements, had always been primarily aimed at children, centering around moral conflicts that were (sorry about this) black and white. Perhaps aware that their audience, and the world around them, was growing up, or perhaps as a result of the show's growing popularity with viewers of all ages, the Doctor Who creative team made a conscious effort to give the series an edgier style, while exploring more complicated, and often socially relevant, ethical dilemmas. Media watchdogs cried foul (though their complaints would be laughable to anyone raised on American television), but the show would continue to grow with its audience over the years, changing and keeping up with the times
The Essentials
The Silurians (Season 7, Episode 2)
Though probably a bit of a shock for those viewers coming from Hartnell and Troughton, Doctor Whos seventh season, with its mature tone, modern feel and moral grey areas, might feel surprisingly familiar to fans of the current series. And its second episode, The Silurians, finds that season at its peak. Much more than garden variety monsters of the week, the subterranean reptiles of the title are a far cry from the pure malevolence of the Daleks or Cybermen, and their complex nature allows viewers one of the first, and most significant, insights into the Doctors alien perspective: human life is not the only life worth saving and, sometimes, not even the most deserving. The Doctors relationship with the Brigadier, though always a slightly tense one rooted in genuine affection and respect, is at its most three-dimensional and layered here, highlighting the contrast of military vs. scientific mind that served as an ongoing background conflict throughout the Pertwee era. Some viewers may have trouble overlooking the regrettable rubber costumes and poor production value, and the shocking ending will be undercut by advanced knowledge of the Silurians reappearances in both the classic and current series. Nonetheless, thoroughly enjoyable and engrossing, The Silurians stands out as representing the Pertwee era, and classic Doctor Who, at its finest.
The Claws of Axos (Season 8, Episode 3) 
Every Sherlock Holmes must have his Moriarty, so in Doctor Whos eighth season, viewers met The Master: another renegade Time Lord and the Doctors arch-nemesis. While many would contend that Terror of the Autons, the serial that introduced him, is the more essential, The Claws of Axos, in addition to just being a better story, provides deeper insight into the true nature of the Doctor/Master relationship. The reluctant partnership they must enter into to defeat the Axon threat allows them to move beyond their usual adversarial dynamic, revealing their grudging mutual admiration, while also throwing their differences and, perhaps more importantly, their similarities into stark relief. As the Master, Roger Delgado oozes his trademark sociopathic charm, without ever descending into the sort of mustache twirling villainy some of the other serials sometimes required of him. And Pertwee is provided with the dramatic space to give us a rare glimpse of his Doctors darker side. While his desperation to escape his exile on Earth was always apparent, the climactic events of Claws of Axos and Pertwees cool, modulated performance raise uneasy questions about just how far hes willing to go, and how much hes willing to sacrifice, in order to regain his freedom.
The Exceptional
Day of the Daleks (Season 9, Episode 1)
Mystifyingly maligned by the majority of classic Doctor Who fans, its true that this taut little tale of temporal paradox contributes nothing to the mythic annals of Dalek lore. And when one considers that this serial marked the Daleks first appearance on the program in four years, its perhaps understandable that, at the time, fans may have been disappointed by their relatively slight return. But strip away any great expectations, and whats left is a tightly wound action-adventure yarn that manages to be, all at once, a ghost story, a sidewinding sci-fi thriller, and a political parable. Day of the Daleks is also vintage Pertwee, giving his Doctor ample opportunity to do the things he does best: dive head first into the action with fists flying and guns blazing, and speak truth to power, whether with smug charm, impatient condescension, or indignant outrage. Fans of Steven Moffats timey-wimey wibbley-wobbley narrative twines will find their roots here. Those that find them irksome (though, if you do, its something of a mystery as to why youre watching a time travel show to begin with) may want to skip this one.
The Green Death (Season 10, Episode 5)
Companions come and companions go. Its commonplace in Doctor Who. On occasion, in the classic series, their departures were momentous events (the poetic and touching final moments of Dalek Invasion of Earth, for example, or the Doctors short, forced farewells to Jamie and Zoe at the end of The War Games, which are warm and heartbreaking despite their brevity), but most of the time they felt a bit rushed, and even in the most dramatic cases, they were almost always sudden. The Green Death is something different. An environmentally conscious, politically pointed techno-fable about exploited coal miners being terrorized by mutant monsters born of industrial pollution, on the face of it, its good, solid Pertwee-era Doctor Who. But underneath the usual sci-fi adventure trappings, it is also the story of the Doctor slowly losing one of his companions. For the first time in the program, we see a companion (Katy Mannings Jo Grant) gradually coming to the decision to part ways with the Doctor and live her own life. And we see the Doctor growing increasingly aware of, and troubled by, her impending and inevitable departure. Giant maggots, hyper-intelligent supercomputers and brainwashed bureaucrats abound, all of which the Doctor takes on with his usual dashing poise. But after a patient, backgrounded dramatic build, Jos announcement of her decision in the last, quiet minutes of the serial, leave him shaken in a way viewers had never seen before. And wouldnt see again for some time
The Expository:
The Three Doctors (Season 10, Episode 1)
To mark Doctor Whos tenth anniversary, in 1973, the Doctor Who creative team decided to celebrate with an anniversary special that would finally put an end to the Doctors exile on Earth, throw some light on the dark recesses of the Time Lords shadowy history, and even bring William Hartnell and Patrick Troughton back to reprise their roles, uniting all three Doctors in a fight against a powerful threat to all of time and space! Unfortunately, The Three Doctors is not very good. In fact, its a bit of a chore to sit through. Overly long, meandering and dull, riddled with continuity problems (as all multi-Doctor stories are), and featuring some of the most embarrassing-looking monsters in the series' history (and that's saying a lot!), it is sadly, for such a pivotal story - one of the low-points of Pertwees tenure. While its hard for any Doctor Who fan to not get a bit giddy at the idea of a multi-Doctor adventure, the First and Second Doctors spend most of the serial sidelined, and its disappointing to realize how little the story would suffer were they completely removed. Troughton keeps things buoyant enough, especially when sparring with Pertwee, but hes really little more than comic relief, displaying none of the complexities that made his Doctor so memorable. And Hartnell was, by this time, quite old and very ill, requiring that his role be little more than a brief, suitably grouchy cameo appearance on the TARDIS scanner (i.e. reading his lines off a teleprompter in a pre-recorded studio session). Theres no denying that Three Doctors is a milepost in the series history, but like most mileposts, taken by itself, its not much to look at.
The Execrable
Throughout his five years in the role, Pertwees Doctor saw quite a few ups and downs. His first year, Season 7, remains one of the series best, but Ill probably incur the wrath of many classic Who fans when I say that his last, Season 11, is probably one of the worst. Despite the always significant regeneration at its end, despite the debut of the Sontarans, despite the introduction of Elisabeth Sladens Sarah Jane Smith, its a weary, dreary run of serials that seems short on both inspiration and investment. The departures of Katy Manning and producer Barry Letts and, more significantly, the death of Roger Delgado (who played The Master) the previous year cast a pall over the program behind the scenes and its palpable on screen. None of the individual serials are as outrageously bad as Hartnells The Gunfighters, but collectively, they make for a sluggish crawl towards the end. A Few Extras The aforementioned Season 7 is worth viewing in its entirety. Season 8s The Daemons was a personal favorite of Pertwees, and feels a bit like Doctor Whos take on Hammer horror. And Season 10s Carnival of Monsters is a popular fan favorite from the masterful mind of one of classic Doctor Whos mainstay writers, Robert Holmes.