Phase One: Probe Insertion

By now you were feeling so horny that you answered without hesitation, "Yes, I'm ready," and then eagerly hopped up onto the table and lied back. Shortly afterward you felt some clamps fasten around your ankles, thighs, wrists, upper arms and torso, and the table begin to move. However, instead of hoisting you into some kind of bizarre yoga position like you'd experienced in the medical bay, this one simply began to form a Y-shape, spreading your legs and simultaneously lifting and bending at the knee.

The result reminded you of old-fashioned stirrup-style tables that doctors once used for gynecological exams or childbirth way back in the early 2000's. By the mid-21st century, 3D scanning technology had become readily available to anyone, and combined with the advances in AI diagnosis, home medical check-ups largely replaced the need for preventative screenings with actual doctors. Meanwhile, advances in fetal monitoring had discovered that birthing from a squatting or kneeling position was safer than the reclined position. As a result, the tables with stirrups were almost never found anywhere but in museums.

The Grey moved into a position between your legs and started examining your anus. He reached up and pulled down a small hose from the apparatus hanging over the table, and then he began touching it around your sphincter. It tickled, and you would have squirmed away if not for your limbs and waist being secured. After several seconds of the teasing touches around your anus, he stopped.

"Your rear orifice is unusually tight for a humanoid of your size," observed the Grey researcher. "We'll need to address that first." Then without warning, he suddenly inserted the small hose into your anus, the only part of your human anatomy down there that they'd been able to save. " This won't take long. Just relax," he added.

Suddenly, you saw the length of the hose begin to glow dimly, and you felt it begin to pulse. At first the throbbing was barely detectable, but soon it became stronger and at the same time, it felt like the tube was steadily increasing in diameter as well. The tube continued glowing more and more brightly and eventually the throbbing pulses became so intense that you could barely handle it. The sensation was driving you crazy, and you would definitely have an orgasm if this kept up much longer. However, before that happened, the pulses suddenly stopped and the hose went dark.

The Grey removed the small tube and it immediately retracted upward. Then he pulled down the large dildo-shaped primary probe, and inserted it into your rectum and then further. And further. And still further. "Um...how deep does it have to go?" you asked.

"The optimal measurement point varies between species. He moved his hand across a panel and displayed a live 3D view of your body, then zoomed in on the torso area showing your transplanted Cuni colon. It was similar to a human version, but the lower bend that normally differentiated the rectum from the sigmoid colon wasn't there and instead it was mostly straight from the anus for quite a distance. "For Cunis, the optimal point is usually near this," he added and highlighted a section just below the first main bend separating what would be the called the traverse colon and descending colon in humans. "We will start there and adjust the probe insertion depth as needed."

In awe, you continued watching the image as the long, thick probe penetrated still further. The deeper it went, the more amazing it felt, and you realized that Cuni colons must be lined with a significant number of nerves that sent stimulus to pleasure centers in the brain. Finally, the probe reached the bend and slightly shifted back and forth a few times before coming to rest just shy of the bend.

"Optimal measurement point is confirmed," announced the Grey researcher. "Next we will insert the secondary probe."

The alien repeated the process with the small tube, dancing it over your labia. However, this time he didn't insert it and instead slid the second probe directly into your cunt. Despite it's thick diameter, it seemed to slide in rather easily. You watched as it easily glided in the full length of your transplanted vagina, expecting it to stop at the cervix. However, it continued to press in still further. As it began to **** open your cervix, it sent shockwaves of pleasure through your pelvis. "Oh fuck!" you cried out. "How....deep...does this one...need to go?" you panted.

"The secondary probe needs to stay in close proximity to the primary probe, so we will be inserting it as far as possible. Per design, this probe allows for full uterine insertion. Just relax a bit more. It's almost in position."

As the secondary probe continued going deeper into your womb, the sensation of it sliding through your vagina, and forcing past your cervix was almost unbearable. Meanwhile, you still felt tingles along the length of your colon from the other probe and the connecting hose as well. Only after the secondary probe touched the deepest wall of your uterus did it finally stop.

"After we confirm the baseline measurements, the testing phase will begin," announced the Grey researcher, and he began looking at another console.

While he did, you wondered how long would you'd be able to endure this. The tests hadn't even started yet, but you were already on the verge of having a massive orgasm, probably several before this ended.