Mario & Flybro: The Mysterious Mansion is a fan-made concept, and thus has no official history or production details. Its gameplay is imagined to be a blend of 3D platforming (similar to Super Mario 64) and potentially puzzle elements. The inclusion of 'Flybro' suggests a new character or a unique mechanic, perhaps involving flight or aerial maneuvers.  Hypothetically, a small team of independent game developers or a dedicated group of modders could have created such a game, utilizing ROM hacking or game development tools.

Mario & Flybro: The Mysterious Mansion

Majora's Mask Redux v2.0