A lot of alternate and unproduced figures came out of Asia in the early 2000's. For a time, it seemed every single figure Hasbro took to retail had at least one Asian variant. In time, though, this slowed down. It might have been tighter factory controls. Or, it may simply have been a function of Hasbro drastically reducing their product line and the diminished volume allowed for stronger quality control at the source.
First up is the Alley Viper. Ostensibly, this figure isn't much different from the production figure. The blue is a little brighter. Unaccessorized, the figures are rather bland. But, it's not hard to find Alley Viper gear from this era (there were a lot of them released) so if you can track down the figures, they aren't hard to get up to speed in terms of gear.
The Viper figure, though, has some significant changes. While the base colors are slightly brighter than the production figure, it is the black face mask that is the most striking difference. Hasbro never released a Viper with a black faceplate and it is a powerful look for the figure. In the right context, it could have been a very strong Viper repaint.
The Viper figures were fairly popular for a while and tended to fetch decent prices. The Alley Vipers, though, did not fare as well. Today, you still see the Vipers for sale, often for significant amounts. But, the Alley Viper variant remains relatively obscure.