If you're any stretch at all of a fan of Douglas Adams or his Hitchhiker's Guide to the Galaxy, you're either already a fan of Dr. Who or may come across this episode at some point or another. It's actually a great place to start for a (relative) newcomer to the original series, as the story gives a strong combination of the humor, camp, pathos and excitement that Doctor Who provides at its finest. So hopefully this is the "some point".
As someone who's only seen two or three episodes of Dr. Who- both 'old' and 'new'- this is top of the crop. Adams gets how to make it an interesting mystery for the good Doctor Tom Baker to figure out the problem of Calufrax with the section of the key of time they need. It's got some hilarious moments and lines of dialog that are quintessential Adams ("Plank. Theory: simple. Walk along it. Come to edge. Fall off 1000 feet. Die!"), and some cool looking creatures, and of course the Captain, who kicks ass as a dastardly Dr. Who villain.
Must, must see, all four parts of course.