Is "Banjo-Threeie" a Real GameCube Game? No — It's a Myth

No, there is no game called "Banjo-Threeie" on GameCube (or any platform).

You may be thinking of Banjo-Kazooie: Grunty's Revenge, released on Game Boy Advance in 2003 (not GameCube). The main series entries are:

• Banjo-Kazooie (N64)
• Banjo-Tooie (N64)
• Banjo-Kazooie: Nuts & Bolts (Xbox 360)

If you meant a different title, let me know!