Kirby 64 Promo Game @ Lost Data
It's a simple memory game. Upon completion, the player is able to download a Kirby wallpaper. (It appears in the same download area as Toonami wallpapers, so it wasn't a big secret.)
Unfortunately, the Wayback Machine failed to save the wallpaper. However, at least one website saved the file and noted where it came from, and so we know which wallpaper was offered by Toonami.
(Click to view 1024x768 image.)
I don't remember this game from back then. Of course, the Toonami homepage wasn't very interesting until the Intruder premiered and Reactor came online. I probably didn't visit enough...
