Hmm, digging in to the various forums again, that Duck Hunt Dog source photo is being called out as not existing until today and possibly reverse-engineered.
The Mr. Game and Watch clipping thing seems inconclusive given the resolution of the "leak", but I would think someone who went through the trouble of faking a bunch of models wouldn't **** up like that.
But over all who knows. I'm still leaning toward legit, if only because of the screwy logic of the final roster, which doesn't really adhere to any heated fan wishes. There's no lobby for Bowser Jr. or Dark Pit, really. If this is fake, it will nonetheless go down in some form of sad history as one of the more agitating fakes of all time.
Regarding Duck Hunt Dog, I think it would be a pretty natural choice. I saw some post during this dig that pointed out that Melee had a retro hardware based character in the form of Game and Watch, and Brawl had ROB. Duck Hunt would fill this roll pretty well, as I think it is the most widely known zapper game. (Gotta assume it takes credence over the Super Scope or Virtual Boy)