To unlock the secret character Huey, the player would normally need to possess Mickey's Speedway USA on the Game Boy Color with data and use the Nintendo 64 Transfer Pak to transfer information to the N64 version.
This hack unlocks that exclusive character without requiring a Transfer Pak and Game Boy Color game.
Database match: Mickey's Speedway USA (USA)
Database: No-Intro: Nintendo 64 (v. 20210220-053642)
File/ROM SHA-1: 507341C0A40CA3E9A7CEE969B396EE53FACFB548
File/ROM CRC32: 2D4F8F1B