Through all the pleasurable sucking and pumping, Josh can feel something else: an odd pressure in his butt. It's not just the fluid being pumped into him--he can feel that too--it feels more like his entire ass is being inflated.
He twists around, trying to get a better look at his backside. It doesn't look any different. Maybe a bit...rounder? No, it must just be the angle and the light. The tube around his dick gives an especially hard pull, and Josh gasps in pleasure. It's so hard to think! "I've got to concentrate!" he says to himself. He looks back at his ass again. Yes, it's definitely rounder, filling out. And it feels amazing! He can feel his butt growing, becoming larger. It's like getting a boner, but, instead of his cock slowly enlarging, it's his butt!
He looks back at Ted, who's continuing to jerk his big member. "What are you doing to me?! You--" Josh breaks off, unable to hold back a moan of pleasure, "--you madman!"
"I already told you," Ted replies, "I'm turning you into a pig. That viscous mixture being pumped into your anus is a special mutagenic mixture that I've tweaked to give you a more attractive form. My own creation. It's changing you from the inside out, starting with the part of the body closest to the insertion site. Soon it will become absorbed into your body and the changes will spread. I think you look very cute with a big pig's ass! Ah, I think the next change is starting!"