Carnival of Monsters (1973)
Jon Pertwee, Katy Manning, Leslie Dwyer
4 25 minute episodes
Plot: the Doctor finds himself trapped in an inter-galactic peepshow, where different life-forms are unwittingly caged in small worldlets. He has to save himself and the other prisoners as the peepshow machine disintegrates.
A neat mix of suspense, comedy (particularly the carnival characters), imaginative story-line and the social comment prevalent in the Jon Pertwee years. Perhaps some of the special effects are tacky . . . but this is classic fun.