Jingle, jingle.
The only... or at least the easiest way into Bowser's castle in the Mushroom Kingdom. Each of his minions carried one of the keys:
- Giant Beetle - Key with "I"
- Womp King - Key with "W"
- King Bob-omb - Key with "B"
- Eyerok - Key with "E"
- Giant Centipede - Key with "C"
- Giant Robot - Key with "R"
- Giant Piranha Plant - Key with "V"
The keys fit neatly into a series of locks around a Warp Pipe in the bottom of the moat around the castle.