Castle world

The 'Castle' world was planned to be the final world in Banjo-Tooie, but was ultimately cut during development due to time constraints. Only a concept design and assets were produced, before the world was cut-down and re-purposed into Cauldron Keep. Unlike Cauldron Keep, this earlier incarnation was to feature 10 Jiggies, Mumbo along with several Mumbo Pads, and a single Jamjars hatch. The addition of this world to the nine already in the game (including Isle o' Hags) would've lead to a total of 100 Jiggies in Banjo-Tooie, matching the total amount of Jiggies found in its predecessor, Banjo-Kazooie.

The theme of the level would have been an old, and extremely large stone castle in the process of being converted into a high-tech metallic stronghold, with signs of construction strewn about the level. A graveyard would have been located at the back of the castle, with a crypt housing a character named 'Mrs. Ghost', and a haunted suit of armour. Cannons at the top of the castle would fire down upon Banjo and Kazooie. Gruntilda herself would be housed in the central tower of the castle, seemingly a new and modern addition to the castle that clashes with the crumbling stone architecture of the main keep.

Warp Pads throughout the world would initially be disabled. They would be covered with a translucent dome, which would retract with the press of a nearby switch. Once a generator in the castle's Teleport Power Room had been activated, indicator lights on the base of Warp Pads would change from red to green, indicating that they can be used.

Mumbo was to be heavily featured within the level, and would have been used to initially gain access to the castle, and activate the Warp Pads by powering a generator. A room containing a large electrified floor required Mumbo to disable another power generator to deactivate the floor. A seed could be planted on one of the castle's turrets, and grown by Mumbo's spell into a beanstalk leading to Cloud Cuckooland. Another turret contains a Raven's Egg, which Mumbo could hatch. Mumbo's Skull would have been located be to the right hand side of the castle as Banjo entered the level. Mumbo could enter the level via stepping stones before the drawbridge is lowered.

Some aspects of the original design are present in Cauldron Keep; a laser mesh portcullis, a purple acidic moat, and an additional Jiggy challenge requirement to access the final battle against Gruntilda.

Jiggies

 * 1) Laser Grid: There is a circular room called the 'Treasure Chamber' (Not to be confused with the Treasure Chamber in Mayahem Temple) where there are lasers criss-crossing along the floor. On one area of the room, there is a podium with a Jiggy on it. Either Banjo, Kazooie or the pair of them would enter this room directly from the outside (in the same position as what would become The Gatehouse). It is presumed that either Kazooie's Glide maneuvre or just using Flap Flip would be needed to traverse the grid without taking damage to reach the Jiggy. Banjo on his own can also view this room with the use of Shack Pack. However, he cannot perform the puzzle via this method as his access to the main room is cut off by viewing glass.
 * 2) Top of the Castle: There is a jiggy in the cone above the central pillar on top of the castle. The cone is glass at the tip of the cone which can be shattered. Whether the shattering would be caused by a Beak Bomb or a switch is unknown.
 * 3) Glide to the Alcove: On top half of the 'Glide Tower' is a Kazooie Switch which must be pressed to open up a door covering an alcove lower in the Glide Tower. This would then presumably keep the door open even if Kazooie were to step off the Kazooie Switch. If this is the case, Kazooie could fly down using her glide maneuvre to reach the Jiggy.

Areas

 * Castle Exterior
 * Graveyard
 * Crypt
 * Gatehouse
 * Grand Hall
 * Dungeon
 * Cells
 * Dark Tower
 * Glide Tower
 * Haunted Tower
 * Gruntilda's Tower
 * Treasure Chamber
 * Rooftops
 * Firing Range
 * Electric Floor Room
 * Armoury
 * Teleport Power Room

Trivia

 * There are at least 18 pages of drawings for this level, but only 5 are shown in the tweet (#1, #7, #10, #11 and #18)
 * Drawings seem to have been dated in an unusual order. First #11 on the 4th Nov 1999, then #10 on the 5th, then #7 and #18 on the 8th and finally #1 on the 9th