In a past JFPN Chat, Scott Walters discovered a very interesting item at Yahoo Auctions Brazil. It was for a Street Fighter Alpha for the Jaguar.
The text in the auction roughly translated to:
"Cartridge Street Fighter Alpha for Atari Jaguar, with box
and manual. Perfect conversion of the Arcade. Made in
1998 for the Hasbro Interactive, this cartridge is part of the
new launchings for the Jaguar. Extremely rare, exactly in
the United States"
A look at these pics provided by the seller, and you will probably think it is simply a bad Photoshop job done as a hoax. But, people brought up interesting points on Jaguar Interactive II about many pirate/aftermarket carts which were and still are produced in Brazil, examples being the games Street Fighter 2 and Mortal Kombat 3 for the Sega Master System. Tec Toy, the maker of the above titles, also released a Duke Nukem 3D for the Sega Genesis (A decent port, too, as can be played on emulators). So, this cart is not totally out of the question as to being real or fake. Marshall W. Carter e-mailed the seller, and:
"He replied and basically stated that he was surprised that I did not know about pirated Jaguar games..."
No one has been aware of any kind of Jaguar pirate carts. Whether it was fake or not was never proved. However, on one note, the user's auction handle and the link to the original auction has been removed, leading everyone to be inclined that it was indeed a fake.