You giggle a little bit as you click the "monkey" option, still pretty sure this is a prank or something. You with a monkey tail, lol.
Then a stretching feeling runs down your spine and you sit up straight. Your eyes go wide as you feel your butt and the seat of your pants from a new angle, and then several angles in quick succession. Some ... part of you is poking around down there. Oh shit this is really happening!
You stand up and pull the back of your pants down and see a thick black-furred limb sticking down into them. You moan as can feel it expanding down your right pant leg! The stretching feeling stops, and you reach down and grab the base of your tail right below your butt. The feeling of your palm and feeling surges up your back and into your brain, and you gasp. You gently lift your new tail up out of your pants to hang behind them in the open air. You're amazed by how long it is and grab the other end with your other hand. The feeling of two hands through your new fur on an unfamiliar body part is mesmerizing you. You stare hypnotically for about four seconds and then let go and shake your head to come back to reality. You look back at the Chronivac and let it sink in that this IS reality: the device actually gave you a real-life monkey tail! You'd fantasized about something like this but never actually thought it would happen. You look back at your tail one more time and wave it back and forth. It's really strong and dextrous. You feel like you could wrap it around something easily. A desk drawer catches your glance so you wrap your tail around the handle and pull the drawer open, marveling at your newfound power.
You look back to the Chronivac grinning, relishing the feeling of your new tail swaying around behind you. This device can change bodies in seconds. You start thinking about more serious ways to use it, ways that could majorly change your life. This is going to be AWESOME.