Meglos is a good episode, and Tom Baker does an excellent job playing the Doctor possessed by the eponymous monster. It even looks pretty good when Meglos has taken over someone's body, and they briefly become all green and spiky. But theres no skating around the fact that at the end of the day, the criminal mastermind of this serial is a talking cactus. Which is, you know, threatening and all, with its spikes and impressive water retention skills, but not exactly the stuff that memorable villains are made of.