It's a dorky, joyful celebration of the beloved Nintendo 64 platformer. Erik the Dud touches on the storyline of the game — wherein dopey bear Banjo and sassy bird Kazooie (who lives in Banjo's backpack) need to save Banjo's sister — really an excuse to send the player through the game's wacky world. He also touches on the finer points of BK, such as jiggly collection, specific attack names, and weird quirks of the game's structure.
The song samples several Banjo-Kazooie tracks (from Grant Kirkhope's OST), as well as the most memorable sound effects, like antagonist Gruntilda's screeches.
There's a playfulness to Erik the Dud's style. This is fan art from a delightfully absurd '90s game, and the song captures that earnestness and goofiness without a hint of irony. Banjo would have loved it.