When Eddie tells the monsters about swapping teeny pets - free toys that come in cereal packets - Fiend becomes addicted, determined to build the biggest collection of teeny pets ever. Meanwhile, it gives Kate and Nick the idea to swap roles - leading to even more chaos in the household.

When the monsters are left home alone while the family visit Kate's parents, they receive a surprise visit from a couple of burglars. The burglars certainly get more than they bargained for as the monsters defend the Carlson house in true monster style.

Nick and Kate go out for dinner, leaving a new babysitter in charge. At first it seems Mrs Travers just wants to spoil Eddie and Angela's Friday night fun - but it turns out she is a monster catcher! How will they stop her from seeing the monsters - especially when Haggis thinks he doesn't exist and actually wants to be seen?