My mind is blown: so, long story short, Sega was looking to replace Sonic as the face of the company for the Saturn era. Sonic came from an internal design competition at Sega, so they did that again, but this time, instead of one game, it was three: Bug!, Astal, and Clockwork Knight. When the smoke cleared, one of those three would become Sega's mascot for the Saturn.
And, well, none of them really set the world on fire, leading Sega to back off and refocus on Sonic. It was particularly a bummer for Clockwork Knight, which was rushed to market with effectively half the game done. So, they pulled a Sonic 3 & Knuckles, producing a "sequel" that was just the rest of the game. To make up for it, Clockwork Knight 2's intro FMV is a super upbeat music video effectively recapping Clockwork Knight 1's meager story.
As it turns out: it's way more than that! The entire first game is hidden in Clockwork Knight 2, accessible through an unlock code that was only just discovered. Presumably this info was meant to be officially disseminated years ago but never got out there until it was forcibly dug out of the data in the modern era.