Dopplegangers were created by the Magus during the Infinity War storyline. During that time the Magus (the manifistation of the pruged Evil of Adam Warlock) created creatures or "copies" of many of Marvel's Super Heroes. (if memory serves me correctly each was actually a cosmic cube of sorts, but in honesty I am foggy about that part). Most of these copies disappeared after that story arc, however for one reason or another (popularity?) The doppleganger Spiderman remained and was featured in some Spiderman Story lines (I believe the first being with Demogoblin) but came to promonince during the Maximum Carnage story arc where he teamed with Carnage, Shriek, Carion, and Demogoblin.
Comments
That's not Parker.
His name is doppelganger and he is very offended
If I'm wrong tell me
Yes as @Marvelfan30 said, there is already a mutant (mutated) Spider-Man in the comics