Biff stumbled backwards and crashed into a shelving unit. Buckets, mops, boxes, and plastic jugs fell crashing to the floor around him.
He leaned against the wall, spread his legs apart, and craned his body forward, trying to look at the alien organ gaping between his legs. He couldn't believe what he was seeing, and feeling, and his mind kept rebelling against it.
Meanwhile, Sarah noticed the large dildo on the floor. She reached down and picked it up. Other than feeling slightly warm, it seemed like nothing more than a large piece of rubbery plastic. She lifted it up and examined it. It had a large, sculpted rubber ballsack in the middle and two large penises extending in opposite directions. Each one looked quite large - probably about the same size as Biff's cock had been.
As she examined it, she felt herself getting warmer and wetter between her legs. She had a sudden urge to start masturbating with it. While Biff stood in the corner, staring bewildered at the pussy between his thighs, Sarah slowly started stroking one end of the large dildo against her clitoris.
Within moments, she was sliding the large dildo inside her sopping pussy. It felt amazing, far better than masturbation normally felt. She pushed it deeper and deeper, feeling it fill her inside. She tried to pull it back a little, so she could slide it in again, but it seemed to be stuck or something. She slid her hand down to the other shaft to get a better grip, and then she gasped. She could feel it! Not just the dildo inside her, but the shaft of the end that was sticking out.
Sarah looked down and saw that a large, erect penis was sticking out of her crotch. As she looked, the other shaft slid all the way up inside her and the flesh around her pussy merged with the dildo. The plastic of the dildo became softer and turned into skin. The tip of the cock grew darker.
Sarah tried grabbing the dick with both hands to pull it out, but nothing happened. She gently probed around the ball-sack with her fingers but couldn't find a seam between her body and the dildo. Instead, much to her surprise, she felt the heavy swinging of balls... her balls... between her legs.
She kept on feeling hornier and hornier, though. She glanced up at Biff, wondering if he could help, but saw him still groping at his pussy, looking as if he were about to cry. The sight of the pussy sent a shiver through Sarah's cock and up her spine. The sight of Biff's sleek, hairless body and well-defined muscles turned her on even more. Gently, she started to stroke her new cock, and she moaned slightly at the amazing sensations that she got.
Sarah started walking towards Biff, stroking her cock faster and faster with one hand, while her other hand fondled her breasts and twirled around her nipples. Biff looked up, and gasped again.
"Sarah, you have... you have..." stammered Biff.
"Biff, I want to put this inside you," said Sarah.
"No way!" said Biff. He still couldn't wrap his mind around the fact that there was a pussy between his legs. Seeing his girlfriend stroking a large dick in her groin was hurting his brain. And there was zero chance that he was letting anyone stick anything inside him right now!
"Please..." moaned Sarah, as she stroked her cock faster and faster, moving closer and closer to Biff.
"No!" Biff said. "Please, no!"
"Oh... Biff.... I'm getting so close..." moaned Sarah, now merely inches away. She pushed his hand to the side and started to guide her dick towards his pussy.
"Please, no!" said Biff again. He covered his pussy with both hands and slid to the floor, trying to avoid getting penetrated.
"Oh my god, it's happening!" said Sarah, stroking herself faster and faster. Her cock was now inches from Biff's face, and she leaned her other hand on the wall behind him.
"Oh!" she cried, and her whole body bucked as a stream of milky white fluid shot out of her cock, all over Biff's face and chest, into his hair and onto the wall behind him. "Oh god!"
Biff tried to cover his face, in vain - he only ended up getting some of the fluid sprayed in his eyes, blinding him.
Sarah stepped back, panting, beads of sweat running down her face and her breasts. She felt the cock losing sensation in her hand. She looked down at Biff, and saw the white, sticky fluid all over his face and hair, dripping into his eyes, and she felt her arousal fade like morning dew.
She looked down at her crotch and noticed that the cock once again had a glossy, plastic sheen to it. Somehow it looked even bigger than it had before, but the sensation was fading fast. She gave it a quick tug and it fell away from her crotch.
Looking down, Sarah saw that the double-ended dildo was a dildo once more. She felt between her legs and found her pussy, moist but otherwise back to normal. She looked at the dildo again; instead of both shafts being roughly the same size, one was now distinctly larger than the other. Not by a lot, but by a couple of inches - it was also thicker around.
She looked down at Biff again, desperately covering his pussy while trying to wipe jizz out of his eyes, and she felt a wave of disgust pass through her. Was he crying? For some reason, she didn't seem to care. She dropped the dildo between his legs, put her clothes back on, and left the janitor's office without a word. Biff sat naked in the corner, trying to wrap his mind around what had just happened.
