Banjo-Kazooie: The Secret of Spiral Mountain is the forth game in the Banjo-Kazooie Series.
Banjo, Kazooie, Tooty, Klungo, and Mumbo Jumbo are relaxing at Banjo's house, when LOG arrives in panic saying that Grunty has escaped from the video game factory! Banjo and Kazooie start to race off to fight Grunty, but Klungo, Tooty, and Mumbo tag along to help, Jamjars and Bottles are missing, so Speccy, Bottles' Son, teaches the duo moves, along with two Surprise Appearances...
- Banjo - A heroic bear that is the second strongest character, only beaten by Klungo.
- Kazooie - A rather loud bird that spends her time in Banjo's (Or Tooty's, Mumbo's and Klungo's) backpack, she is only controlled when Banjo/Tooty\Mumbo/Klungo uses moves.
- Tooty - Banjo's sister who finally makes a playable appearance, she can be controlled in Co-op and Vs. Mode.
- Mumbo Jumbo - A shaman who has a skull for a head thanks to Grunty, He, like Tooty, can be controlled in Co-op and Vs. Mode.
- Klungo - Grunty's former minion turned good, he is the strongest character, and He, like Tooty and Mumbo, Can be controlled in Co-op and Vs. Mode
- Speccy - Bottles' Son takes Bottles and Jamjars roles from previous games.
- LOG - Lord of Games, owner of a video game factory.
- Grunty - The main villain, appears in her cyborg form and trys to find the treasures of Spiral Mountain's core.
- Donkey Kong and Diddy Kong - Help Speccy teach moves by demonstrating them.
- Mrs. Bottles - Bottles' wife, runs a shop where T.T. Trophies can be traded in.
- Trophy Thomas - A leopard who has blue hair and loves time!
- Jamjars and Bottles - Two moles who were kidnapped by Grunty.
- Humba Wumba - Mumbo's rival who transforms the gang.
- Banjo, Tooty, Klungo, Mumbo - Mushroom, Hedgehog, Beaver, Squirrel.
- Kazooie - Snake, Pyradactal, Bat.
Spiral Mountain - The main area, Banjo, Kazooie, and Tooty live here. Enemies are Toppers and Minjos.
Crystal Cavern - A cave and the first world, the boss of this world is Twinkle Shard, Enemies are Minjos and Boom Boxes.
Lava Lagoon - A lava lake and the second world, the boss of this world is Weldar 2.0, Boom Boxes are the only enemies here.
Earth Cave - A giant indoor garden and the third world, the boss of this world is King Topper, Toppers are the only enemies here
Topsy Turvy Tube - A small tube that is extremely long and the forth world, the boss of this world is Mingella, Minjos are the only enemies here.
Panicy Pipe - A pipe that often shakes and is the fifth world, the boss of this world is Blobbedda, The only enemies here are Rippers.
Grunty's Corner - Grunty's area at the center of the mountain and the final world, the boss here is Grunty, All enemies plus the gruntlings appear here.