Robert Holmes is generally considered
Doctor Who's greatest writer for good reason: he was able to write stories that stayed entertaining through their entire length through great characterization, dialogue, and world-building. But look close enough at many of his stories, and you also find something highly subversive. In fact, if he's not the writer in charge of things, he's very often biting the very hand feeding him (and a hand for which he has obvious affection). Under the many layers of
Caves of Androzani resides a subtle critique of the entire Fifth Doctor era and a sense that Holmes is saying, "
This is how you should have been doing things the last three years."
The Krotons seems a deliberate attempt to re-align the Second Doctor's stories with his characterization, something that rarely happened outside of David Whitaker's scripts.
The Two Doctors barely even hides its contempt, instead reveling in its mockery of the era's over reliance on continuity references and ugly violence.
Carnival of Monsters has self-satirical ideas of its own, albeit of a different sort from those above. But like
Caves, on the surface of its subversion is a terrific adventure yarn, and is a blast to watch without seeing a hint of what's going on underneath.