Clockwise from top-left: Hammer Keychain, Rocket Keychain, Squash Keychain, Pumpkin Keychain.
Keychains, also referred to as Super Cool Keychains, are hidden collectibles in Dr. Lunatic and Dr. Lunatic Supreme With Cheese. There are normally four keychains hidden in each world, the Hammer Keychain, the Rocket Keychain, the Squash Keychain and the Pumpkin Keychain. Each Keychain is based on an object or enemy originating from SPISPOPD.
Effects[]
When collected, a Keychain will be added to the list of keychains currently found for the world it was found in. In the original game, they would then be displayed as part of the player's key ring. In Supreme With Cheese, due to the absence of a key ring, Keychains are displayed as tiny pictures in the pause menu; each picture starts out dark green, but is filled in with a lighter green colour once the respective Keychain is found.
Finding all four Keychains in a world will normally open up a secret level ("Keychain Level") on the hubmap. These Keychain Levels are normally optional and not required for beating the world, although some worlds do but they need to be completed to achieve 100% completion.
SPISPOPD Reference[]
In the original five worlds (Spooky Forest, Dusty Desert, Icy Mountain, Cavernous Caves, Crazy Asylum of Madness) as well as the Expando-Pak worlds (Pygmy Island,The Haunted Mansion and Space Station Loony), Keychain Levels would always include a type of Pumpkin enemy as an ode to SPISPOPD.