Terror of the Zygons is one of those serials that has a reputation. There are a few of these, the stories that are generally considered classics (or the opposite). Usually, even if the story is flawed, it's clear what makes it great.
But Zygons' popularity seems somewhat inexplicable to me. It's a fun yarn, but the idea that it's one of the all-time-greats of Who - particularly in a season including Pyramids, Morbius, and Seeds of Doom is strange.
