One of the reasons why I love classic Doctor Who (maybe even slightly more than new Who) is that every once in awhile, it would integrate influences and/or stories that seemed extremely left of center. I've always had a slight fascination for Buddhist thought - nothing to make me adopt it as a primary belief system, however. Think of me as more of a "cafeteria Buddhist". So seeing Buddhist concepts and themes played out in classic Who are rather interesting; there are three great examples - two of which are by the same author - and which, although having mixed levels of success, are actually pretty decent watching.
The first is 1974's Planet of the Spiders, probably best known as being Jon Pertwee's swan song (as well as introducing the term "regeneration" for the Doctor's changes). Taking place in a Buddhist meditation center, it's pretty much a slightly better-than-standard invasion from another world premise...but interestingly, some of the ideas within the episode are often thought provoking. Much of the action results straight out of the Doctor's arrogance, and there's a large emphasis on this Doctor somehow "paying back" karmically for his actions. (For those not quite into Buddhist thought, there's also a great multi-vehicle chase in the middle of the story). Most of the more exotic philosophy is handled superficially (then-producer Barry Letts was a practicing Buddhist, but took care not to turn it into propaganda). Once we reach the end, when we know the Doctor is going to regenerate, there is a slightly palpable sense of loss - we know the Doctor is dying, and in that moment, he is accepting. It's not one of the greatest Who stories ever made....but is well worth a look.
Flash forward eight years - different producer (John Nathan-Turner); a more scientifically-minded script editor (Christopher H. Bidmead) and a writer with a background in theater (Christopher Bailey) all combined to produce Kinda, which superficially seems to be a colonists-against-indigenous-population tale, but beneath that surface lies a multifaceted tale about identity, sanity, and stillness. It's easy to knock this story for the garish-looking plastic snake (or "the Mara") at the climax; thankfully, this DVD allows you to substitute and equally counterfeit-looking CGI snake. It's not an easy watch, either - part of it is the obvious jungle-on-the-studio-floor set, but it lacks the whiz-and-bang of the new series. What it does have, however, is a slightly more quiet power - it's the kind of episode that will not necessarily be one's favorite, but I think every Who fan should watch this story at least once, to catch a slightly more nuanced take on a familiar story.
Finally, the following year brought a sequel (of sorts) in Snakedance, which (admittedly) is a slightly more straightforward story about the Mara's influence on an entire civilization. Unlike Kinda, this story is not dependent on the use of Buddhist terms - in fact, it could easily be a typical Who tale about a malevolent force on another world. However, one of the nice things about this tale is that like Kinda , it focuses on people's motivations and character.(Interestingly, both Bailey-written tales propose the idea that the Doctor is slightly crazy - after all, there's no extremely overt threat, is there?). Snakedance is a little less of a must-watch, if only because much of the story seems to be rote. However, much like its predecessor, it's the kind of story that really should be seen at least once.
If you're looking for a dead-on adaptation or integration of Buddhist thought into Who...well, none of these stories is perfect. (And in all fairness, I know as much about Buddhism as I do about quantum mechanics). However, these are three Doctor Who stories that deserve a watch...if only because, in tone and execution, they are slightly off-the-beaten-path.