The amazing powers wielded by some of the fan developers out there never ceases to astound me. From the looks of these videos, this game could go toe-to-toe with New Super Mario Bros in terms of raw Mario-ness. But it's the multiple Mario/Super Metroid mash-ups contained here that push this one into the "must have" category for me.
From the looks of these videos, Extra Mario Bros may be an actual game. With that, I'm officially on the hunt to track down a copy. Or some anti-psychotic medication, which ever I can get first.
Thanks Sistermind, who ever you are.