The Third Doctor
The Pertwee Years
At the end of what seemed like an eternity, and the final episode of the Second Doctor serial, "War Games," the Doctor has to call in the Time Lords to return the soldiers to their own time stream at the risk of having to face his own crimes, including the theft of the TARDIS, and after a brief and ill-fated attempt to evade capture the Doctor is found by the Time Lords and is put on trial, he manages to convince them that he has done good and the Doctors sentence is reduced to a forced regeneration, removing Zoe & Jamie's memories of him and disabling the TARDIS stranding him on Earth.
The debut episode of Pertwee's Doctor, sees the TARDIS materializing in a field and the Doctor collapsing out of it, and introduces Liz Shaw(RIP Caroline John,) as well as the brigadier Lethbridge-Stewart and UNIT as mainstay of the series for the majority of the Third Doctor's run. This episode also introduces the binary vascular system (Two Hearts,) into the Doctor Who Mythology as well as the juggernaut that is Bessie. Jon Pertwee is immediately likeable as the Doctor and his interaction with Liz, Jo and Sarah Jane Smith (<3) is charming and paternal fashion. The Third Doctor's tenure introduces what would become a mainstay character to the series in the Master played wonderfully by the late Roger Delgado, a renegade Time Lord who has a history with the Doctor, as well as a mutual Despise and reluctant respect for each other, often working together to solve issues that were usually caused by the Master himself. Nicknamed "the Dandy Doctor," Pertwee wore a colorful ensemble that matched his colorful persona of his Doctor, the Third Doctor, unlike previous and future incarnations, wasn't afraid to solve a dilemma with brief non-lethal violence showing a variety of martial arts abilities.
As for the Third Doctor's stories, the series was forced by budget cuts to maintain the Doctor's exile to Earth, forcing the show runners to find less alien enemies, which I enjoyed more than the bad special effects earlier in the series. This lead to many stories involving the Master, who Pertwee had wonderful chemistry with since the two were friends in real life, as well as more earthly creatures. Pertwee's run introduced the Autons, Silurians and Sontarans into Doctor Who lore and where previous Doctor's always seemed confused or ill-informed about new creatures, the Third Doctor always seemed completely knowledgable of his foes which gave the Doctor a sense of superiority that I actually enjoyed. Eventually the Doctor would be freed from his exile after the events of "the Three Doctors," and his travels through time and space would continue, this however would lead to a cutback on the brigadier's appearances, which disappointed me since he was always a fun character and his chemistry with the Doctor was great.
The Doctor was originally given an assistant in Liz Shaw, a smart, capable and strong female character. So naturally the show runners replaced her with the screaming stereotype that was Jo Grant, who don't get me wrong I liked, but couldn't compare to her successor, Sarah Jane Smith. Sarah Jane would become my favorite companion ever during her travels with the Fourth Doctor, but it was fun to see her origins with the Third, especially combined with the Sontarans, who featured the best costumes to that point in the series and the first series I was truly invested in. Later the Doctor would meet a fury cave monster and Alpha Centauri, A Green one-eyed tentacle thing with a high voice and it was obvious the silly monsters were coming back, but it didn't bother me so much thanks to the wonderful acting ability of Elizabeth Sladen as Sarah Jane.
The Third Doctor's final episode, "Planet of the Spiders," was a silly monster fest with a confusing plot of spider possession and Sparky hands.. or maybe it was just me. For me the serial wasn't sufficient for the departure of a fantastic doctor, but despite the shortcomings, the serial did have one truly great moment, the introduction of Tom Baker as the Fourth Doctor, who immediately snagged the role and ran with it in a way no actor would replicate again until David Tennant thirty years later.
Now once again these are my opinions, share yours in the comments section if you'd like.