The first episode is Robots Everywhere, where Carl is trying to sell the house to a couple. While touring the house they get vaporized by two robots, that come up from behind them. These two then want to buy the house, though Carl feels uncomfortable about this. He tries to convince them it's a bad idea, mentioning the gas leak, but the robots loved all of it, saying gas is an aphrodisiac to them. Marcula reveals he likes robots and lets them stay, multiplying until there were about thirty of them.
The second chapter of Marcula is Sirens, where Carl hears noise next door and investigates, only to find that three sirens, BJ Queen, Chrysanthemum, and John Kruk, have moved in. They seem peaceful, but Carl catches them playing a game, which entails Johns' skin being pulled off, and his muscles being poked with harpoons. Marcula finds Carl outside the house drilling a hole in the wall to watch, but claims he's installing speakers in the bushes. After seeing the game, Carl gets uncomfortable and calls Frylock, only to get his cell phone answering machine. The machine says they're held in a cave in the Mohave Desert.
The third of the trilogy is Couples Skate where the sirens are gone and a huge monsterous creature called Paul is living in the house. This was it for Carl. He decided to go to Marcula's 4040th birthday, in the cave. When he gets there, Carl frees the Aqua Teens, and Marcula gets hit with garlic water by Carl, that Frylock had told him to bring. At that point, ready-to-skate Paul tears Carl in half, in excitement for the couple skate (hence the name of the episode).
The fourth chapter is Vampirus where Marcula returns and bring back from the dead. He brings all the vampires to bite Master Shake and infected him.