Yeah, it's embedded in there, but to access it you have to beat Metroid Fusion
on the GBA, and then do the little GBA-to-GC link deal, and then you can play the original Metroid on the 'Cube.
I haven't done it yet, simply because I got stuck in Fusion and haven't bothered going back to it yet.
In other Nintendo-related news:
Received my first issue of Nintendo Power in years today, thanks to that stupid Zelda disc thing.
Any five-year olds here who want this thing, or should I just throw it in with my sh!tty anime coupons?