"Oooh, the Living Ideal, how interesting." Dr. Terrific giggled. You turned to your girlfriend in shock, Living Ideal was.... a guy. "Babe, why do you wanna be a man?" You asked.
"Actually, the Living Ideal was a shapeshifter, every hundred years or so he decided to take on a new identity, remember Silver-Tongue from the old comics? that was him, in the form of a buxom blonde woman." Dr. Terrific retorted, *sigh* "Me and him had so much fun over the years, when we first met all those years ago we were both on the cusp of adulthood, he would transform into adults so he could buy everyone booze and we'd throw parties in the academy's secret chambers, but that's all in the past." She reminisced. "But as I was saying, 'He' was a shapeshifter, he was born male and didn't fuss over pronouns, sure, but he certainly loved being women too, if your girlfriend wants she can be anything really." Dr. Terrific explained.
"That's really cool, but I kinda just wanted to try being a man." Your girlfriend said, blushing. "Great, no problem, now if you'll press select and step into the chamber I'll turn you into him pronto." Dr. Terrific says excitedly. You stood there silently, you actually didn't have anything to complain about. Sure it was a shock that your girlfriend wanted to try being a man, however, Ideal was.... kinda hot, at least in the form you knew him as, not as bulky and muscular as some of the other heroes, more of a androgynous appearance compared to the others, like a male gymnast, he certainly had the ass of a gymnast you thought.
Being lost in your own thoughts you hadn't noticed your girlfriend had stripped down to her underwear and stepped up into the glass chamber as her curves jiggled for one last time, for now at least. "You ready?" Dr. Terrific asked, "Yeah let's do this." She responds, visibly giddy with excitement. Dr. Terrific pulls a big, important-looking lever on the control panel and immediately a violet light emanates from the chamber with a low hum accompanying it.
You watched in amazement as the machine quickly went to work on your girlfriend. Almost instantly her clitoris could be seen bulging from her panties, she threw her head back in pleasure and leaned against the glass, rubbing her lengthening clitoris, moaning like you've never seen before. Her clitoris stretched and thickened rapidly as it tented her panties, she pulled down her panties to provide easier access as she stroked her growing member, the new cock growing to a fine 8 inches with the girth of a stack of poker chips.
As she jerked herself off her muscles began to grow, her arms, shoulders, chest and legs all broadening significantly as her frame shifted to that of the Living Ideal's. She winced and bit her lip as a pressure from her ovaries began to build up, culminating in a squelchy, wet *POP* as two large testicles emerged from her vagina, cementing her gender transformation. You noticed a light dusting of hair distributing across her/his body as the hair on their head retracted back into their scalp, you heard their jaw crack as their skull reshaped into a more masculine form. the register of the moans began to lower also as his adams' apple began to poke through their throat. he gripped his bra and tore it off, exposing his unchanged D-cup tits and squeezing them vigorously, this turned you on immensely as even Dr. Terrific noticed your growing boner in your jeans, more cracks and grunts could be heard as your girlfriend's hips shifted inwards, giving his bubble butt even less room to work with, he fell on all fours in pure bliss as you could see his voluptuous ass begin to pack itself in a tad more, firming up with muscle while still retaining a feminine quality. He lay down on his back and began to finger his asshole while groping his juicy breasts, that soon changed however as his chest bulked up even more and his breast tissue began to transform into pecs, retracting back into his sexy frame. The humming began to die down as the light slowly faded, your girlfriend oblivious to all of this, continued to eagerly explore every inch of his new body until Dr. Terrific interrupted.
"OK that's enough I don't want jizz all over the chamber." She said while smirking devilishly. She clicked her fingers and your girlfriend disappeared from the chamber and reappeared on the floor next to you, his new body hitting the ground with a light *thud*.
"Woah, what... oh, sorry I got a tad carried away there." Your girlfriend says as he climbs to his feet, despite having a deep baritone voice he still speaks with the same cadence, giving his speech a girly quality to it. As he stands up you notice how much bigger your girlfriend now is than you, standing 6 feet tall and likely double your weight you feel an strange sense of security next to him, your eyes are drawn downwards and you notice his cock is still at full mast, 'God it's big, I knew I was bi but holy shit is this turning me on.' You think to yourself. Your girlfriend turns to you, "Are you OK with this babe? do you maybe wanna turn into a superhero too?" he asks almost shyly.
"I know it's still you in there, I'd love you whatever you looked like." You respond, going on your tip-toes to give him a peck on the cheek, causing him to blush. "Well." Dr. Terrific says, "It seems that you two are quite happy with the changes, unfortunately you are completely buck-naked and while I can teleport matter I cannot create it, I doubt you'll fit your old clothes so I'm gonna have to teleport you guys out of here, where would you like to go?" She asks.
"Back to our place please, we'll figure something out from here." Your girlfriend says
*SNAP*
The two of you suddenly find yourselves back in your bedroom, upon realizing you now have total privacy your girlfriend pushes you on the bed and begins kissing you, he lowers himself onto your lap and straddles you, grinding his erect cock up against you as you squeeze his firm, juicy backside.
"Mmmmm babe, this feels amazing, how do you wanna do this?" He asks in a sensual tone.