Quite enjoyable serial thanks to a creative script and great guest cast.
Among the cast is Ian Marter, who was considered at one time to be Captain Yates. Barry Letts remembered him and cast him here, and was later to finally cast him as a companion to the Fouth Doctor, playing UNIT doctor Harry Sullivan.
Returning to Who are two of my favorite guest stars, Michael Wisher and Peter Halliday, and they play off each other hilariously.
While trapped in the Miniscope, the Doctor and Jo come face-to-face with perhaps the "star" of this story - the Drashig. Obviously a puppet, but still quite effective nonetheless. One of my favorite "monsters."
One of the most "fun" of the Third Doctor stories.
SeaDevil