Yes, by testing out body modification

"Oh my god!" screamed Ron. "I can't take it! It's too big! It's too big!"

"Ron!" I yelled, almost panicking as I saw the expression on his face. "Um, uh, please have the kind of ass of someone with a lot more experience at this!"

Suddenly, Ron's asshole relaxed, and Jess was able to slide the head in. His eyes closed and an angelic smile appeared on his face. "Oh, that's soooo good, babe! I can't believe how good I feel!"

Jess slapped his ass hard. "Yeah, a slut like you needs a good pounding. You know that's what you are, right? A slut?"

He smiled even wider as she slipped another inch into him. "Ooohhh, yeah! I'm a slut for you, babe!"

"Holy shit this is hot," I said. "Um, since you guys don't seem to mind doing this in front of me, do you mind if I take care of myself? Please?"

The demonic glee left Jess's face as she turned to me and smiled sweetly. "Of course you can! You're our guest!" Then she turned back to her boyfriend and slapped his ass several times while pushing a little further in.

I was still sitting on the floor, so I lifted up a bit to pull my pants down and remove my cock. I stroked it lightly as I stared at Jess's body more intently and freely than I ever had before. She really was pretty cute, and my mind was racing at the possibilities. "Hey, Jess? Would you please take off your top?"

"Sure," said Jess as she started to pull her vest top over her head.

"And please have some big ole titties hiding under that top," I mumbled under my breath.

I was shocked, absolutely stunned, as her top popped off and a huge pair of tits slid out of it. They were massive! I started to wonder it this was some trick of bra engineering, but then she took off her bar and two perfectly shaped, gigantic globes bounced freely. I couldn't help jerking my cock harder.

Had her body actually changed just because I said "please"?! That was insane! She hadn't even heard me say it! I looked over the rest of her body. She had always been a cute, girl-next-door type, but she wasn't a super model or anything. She had a little paunch and a pretty flat ass. Of course, her ass was a little extra fascinating right now since it was slowly moving back and forth as she pistoned in and out of Ron's ass. Normally I'd have been pretty happy seeing this girl naked, but now my head was full of possibilities.

"Please have a super fit, but still super curvy body."

Nothing. She didn't change at all. Had she really had those huge breasts all along and just been able to hide them?

"Oh god!" said Ron, his eyes still shut tightly. "I can't believe how deep you're getting!"

I examined the blissful look on his face, which was kind of hilarious. Then I looked back at Jess and my jaw dropped. Her belly was immaculate. Not just no paunch, but a tiny waist with just the right amount of ab definition. As tight as her waist was, her hips somehow flared out perfectly and lead to a bubble butt and some incredible thunder thighs. Her breasts were still huge, but her general chest shape had somehow changed to accentuate them and her tiny waist more. She had the perfect hourglass shape, and it was amazing.

Her powerful thighs seemed more suited to the type of exercise she was doing, and she drove faster into Ron's ass. He moaned deliriously.

These changes had happened when I wasn't looking. Was that how it worked? I looked at my friend, who had always been kinda frail. Based on the position he was in, I whispered, "Please be a tiny, little guy, Ron."

He didn't change. I squeezed my eyes shut and held them that way for a moment, then opened them again. He was much smaller. It was hard to tell with him kneeling/lying on the couch, but he looked several inches shorter, and even less muscular than before. The only thing physically impressive about him was how much **** his ass could take.

"Oh, Jess! This feels so good!" he yelled.

I jerked harder as I looked up at his now insanely hot girlfriend. Her massive breasts swung heavily as she quickly thrust into him. She sneered and said, "Well, don't get used to it. This is just a one time thing."

"No," I said under my breath, "please make this your new favorite thing that neither of you can get enough of!"

"On second thought, we're going to be doing this all the time! You're going to be my little ass whore, and you're going to love it!"

"I do love it! I love it so much, and I love you, babe!"

"I love you too," yelled Jess in an aggressive way that was both angry and really hot. "I love you more than anything, you fucking ass-whore loser! Now take my fat dildo and squeal, piggy!"

I just stared at Jess as her incredible body shook with all her effort. I wasn't even able to keep it quiet as I said, "Please, both of you cum when I do!" Then I came in a huge orgasm that covered their carpet with my jism.

They both came at the same time. Ron went completely limp as his cock spurted out white, sticky ropes onto the floor. Jess's whole body shook as she stopped thrusting and just held his hips for support. Her mouth opened in a sexy 'O' shape.

We all stayed frozen like that for a long time. Eventually Jess pulled her strapon out of his ass with a loud pop and stood up. She looked down at him and sweetly but sternly said, "Come on, stand up."

When my friend stood up, I saw just how much he had changed. He was tiny, several inches shorter than his voluptuous girlfriend now. They'd gone from being a cute couple to him being nowhere near her league.

Jess smiled at me and said, "It's been great having you, but I think we need to get this place cleaned up. Wanna come by again tomorrow so I can kick your ass in the game again?"

"Um, sure." I stood and pulled up my pants.

As I was leaving, Jess turned to Ron and said, "Get these cum stains cleaned up out of the carpet, loser! If you do a good job, I might just fuck you again after dinner."

"Yes, babe!" said Ron happily as I closed the door behind me.