You have a sexual affair with all the men below, and one day you happen to attend a film awards show, and so do they. None of them know that they all had one thing in common: you. And when they all approach you to say hello, they finally realize this.
Premise is, basically, Stan falls through the portal instead of Ford and into the Nightmare Dimension. Bill brainwashes/convinces/tortures him into hating Ford (perhaps his own was an asshole?), and Stan “Piraña” Pines becomes an interdimensional hitman and bounty hunter, tracking down the many Portal Fords and either killing them or delivering them back to Bill to be personally tortured to death.
Bill cannot leave the Nightmare Dimension, so he uses Evil Stan as a personal meat puppet and channels his powers through him, damaging his eye (hence the eyepatch) and accelerating the aging of his body. In exchange for this willing possession, though, Stan can also use some of Bill’s powers (shapeshifting black tentacles!!) to survive on strange planets and even the void of space for a short amount of time.
Not all is angst and violence, I promise! There are plenty of incompetent henchman shenanigans. See, unfortunately for our amoral protagonist, he is still identical to Ford so sometimes he gets confused for the very bounty he’s chasing XDD