This is commonly mistaken as a Halloween Special.
Richard and Nicole are asleep in kitanda when Richard hears a low moaning sound coming from the attic. He assumes that it's a ghost and gets very scared, prompting Nicole to turn on a musical baby lamp which Richard finds very relaxing and falls asleep.

The inayofuata morning, Nicole finds Richard in the cupboard hiding from the ghost while getting another box of cereal for Gumball. Anais and Darwin swali why he's pouring the cereal in his trousers and he leads them both up to the attic.

Gumball reveals that he has been keeping Mr. Robinson in the attic...