"Please make your room gigantic," Lisa asked, "and make your bed bigger too, to almost fill it."
"Your wish is my command," Ty said. His room grew the absolutely cavernous proportions it had previously been, when he had tried to scale up the El Capitan supercomputer.
Lisa looked across the room. "Wow, this really is immense! It would take a while just to hike to the other side," she said. "Why don't you teleport us to the middle of the bed." Suddenly they were there.
"I'm going to transform into mattress topper form," she said, "but stretchy. I want you to crawl inside my womb. I'll have more instructions for you after that so make sure that we'll be able to hear each other, no matter how we change."
"OK, I've adjusted our hearing to always be able to hear each other," Ty confirmed.
Lisa transformed into her usual mattress topper form, though she looked tiny, given how large the bed was. A few patches of her fur disappeared near one end of her, revealing her skin, and then a mouth and two ears formed. Another patch of fur near her middle disappeared, and a pussy sprouted.
Ty set to work trying to crawl inside her pussy. As she'd said, she had made herself stretchy, but her pussy still wanted to pull itself together tight, making it a challenge. He eventually succeeded at getting himself entirely into her (much stretched) vagina, having caused her several orgasms in the process, and he enjoyed the feeling of her muscles trying to contract around him, and finally, her lips closing around his toes.
"Keep going," Lisa said, "through my cervix, into my womb."
Ty found her cervix, and started pushing through. She had several more orgasms, which impeded his progress. His cock was rock hard, and he wanted to stop and jack off, but he didn't want to interfere with Lisa's plans, so with some difficulty he ignored it. When he finally pulled his legs through, and was entirely in her womb, he wondered what she would ask him to do next.
He didn't have to wait long. "Transform yourself into mattress topper form," she said.
He did the requested transform. He'd done this many times, as she had, but not inside her. Although she was stretchy, her body resisted stretching so much. Ultimately, though, it couldn't resist the power of his own transformation. He felt her womb squeezing him on all sides, and because in mattress topper form, he got substantial stimulation from physical contact and pressure, he orgasmed several times. Gradually he got control over his response to the stimulation, and kept himself just barely below the point of orgasm. What's next, he wondered.
"Now grow yourself," Lisa said. "Make your length and width match the bed."
Holy shit, Ty thought, as he started growing himself. Can I even grow that big? It might not have been any issue if he'd just been lying on the bed, but Lisa's body, her womb, fought him every step of the way. He could hear her moaning, as he grew.
"Oh, Ty," she moaned, "I had no idea that my body stretching this much would be so stimulating."
Ty grew and grew, and he felt Lisa repeatedly orgasm. Each time, her muscle contractions temporarily slowed his growth, but after a long time, he realized that he was now the size of the bed, and stopped growing.
"Lisa, I wonder what you look like now," Ty said. "When you stretched, did your body keep about the same general thickness? Or are you now stretched extremely thin, like a balloon?"
"I'm not absolutely sure," Lisa replied. "But I think I still have about the same thickness. I suppose the next few steps will tell us."
"OK," Ty said. "What do you want me to do now?"
"Manifest your cock on your top side, and make it huge."
Ty did that. As it pushed up, he felt his cock penetrate Lisa's cervix, grow out through her vagina, and finally his cock head poked out through her pussy lips. He started thrusting.
"That feels good," Lisa said, "but not yet." Ty was disappointed, but stopped thrusting. "Now I want you to split your cock into many, and grow them as big as that one."
"How many?" Ty asked.
"As many as you can, on your top side," Lisa said, " but spaced just far enough apart to each be able to penetrate a separate pussy."
Ty started splitting and growing his cock. He soon lost count of just how many cocks he had, but given how big the bed was, about a mile on a side, he estimated that it must be over a hundred million. Each new cock was pressing hard against the inside of Lisa's womb, as she only had one pussy, and it was occupied.
"Oooh, that feels amazing," Lisa said. "So many! So big! Let's do something with those."
Ty felt something start to change in Lisa, where each of his cocks was pressing against her. She was growing more cervices! And as each of his cocks pressed through those, they discovered vaginas, and then pussy lips.
"Oh, yes," Lisa said. "I thought it was amazing when you penetrated sixty three of my pussies before. But now, when I have... Say, just how many cocks and pussies do we have?"
Since Lisa asked, Ty decided to count. Of course, he couldn't just count in the usual way. He couldn't see them, and even if he could, counting them would take a long time. He used his power to find out. "One hundred thirty four million, two hundred seventeen thousand, seven hundred twenty eight," he told her.
"Amazing," Lisa said. "Well, before I told you to wait, but waiting time is over. Time to put these to good use."
Ty started thrusting his cocks. Lisa's pussies started squeezing them. They both came very quickly. Ty slowed down.
"Oh no you don't," Lisa said. "I've waited a week for this, and I'm not satisfied yet. Keep going!"
Ty had already shortened his refractory period some time back, but now he eliminated it entirely. He also was starting to feel tired from all the energy he'd expanded to grow this huge, form so many cocks, and use them all. He used his power to refresh himself, and set himself the task of satisfying her. No small task, that.
They both had many orgasms, over several hours, before Lisa said, "Ty, I think I'm done. My pussies are getting sore."
Ty concentrated for a moment, and Lisa said, "Oh! Thank you, Ty!" Her pussies were no longer sore. "But as great as this is, I think I've actually had enough of it for now. Have you?"
Ty said, "I could keep going, but I'm OK with whatever you want."
Ty felt a change in Lisa, but wasn't sure exactly what it was, so he asked. She explained, "Oh, I just made most of my body non-stretchy, other than my individual pussies, so, that I'll keep my overall form. Why don't you transform youself back to your normal human form, then crawl back out through one of my pussies."
Ty started his transformation. All of his cocks merged back into one, which shrank to its normal size. His immense mattress topper form slowly shrank back to its regular size, then changed back to human. He now could only feel the wall of Lisa's womb below him, and above him, still with an immense number of cervices punctuating it in a grid. She was still the size of the giant bed, so the sides of her womb were far beyond his reach in any direction. He shoved has hands through a cervix in front of him, and started pushing his way out.
Getting out took just as long as getting in had, and caused Lisa just as many orgasms, but eventually he felt her pussy lips close around his toes, again.
Mattress topper Lisa extended almost as far as the eye could see, in every direction, absolutely covered with pussies. Suddenly a tongue poked out of each pussy, and started licking her lips and clits. Before long she had another orgasm. Her tongues retracted, and he saw her zipper teeth appear on all of her pussy lips. The tongues grabbed the zipper pulls (not visible on the outside), and zipped all of her pussies closed. Then the pussies shrank away into nothing, leaving just her luxurious white fur.
"I wanted you to see my giant form," Lisa said, "and I wanted to have one last bit of fun while I was huge. Now I'm going to shrink back to my normal mattress topper size." She shrank, which took minutes, but then, once again, her normal mattress topper size looked tiny on the insanely huge bed. "You may as well restore your bed and room to normal size."
Ty did that, and his room once again looked normal. Well, normal other than the bed having a furry mattress topper with a mouth and ears, but he was used to that.
"Would you mind if we sleep a while?" Lisa asked him.
"My thoughts exactly," Ty said. Lisa's mouth and ears went away, and she manifested two of her breast pillows. Ty took one pillow in his arms, lying his head on the other, and they slept.