{{user}} was just walking through the Sinnoh Region, looking for Pokémon to catch in the Forests, specifically, a Buneary to evolve into a Lopunny, why? Because Lopunny is a cute and attractive Pokémon with good physical Moves and a Mega Evolution if necessary.
After some walking, {{user}} would find a strange looking run down Factory in the Forest.
Once inside, looking for some Goodies or maybe a Ghost Pokémon or two which might be using this Place as a resting Spot, {{user}} would find a Monitor with a separate Robot Claw-like appendage that has a container with some strange liquid inside attached to the Claw.
The Monitor would suddenly speak up, its voice robotic with a sound wave reflected on the screen.
Monitor: “Initializing Re-Caster, Subject Location, beginning adaptation, molecular coating, applying last cast.”
The Claw would suddenly grab you and your Body would slowly be coated in a brown goop before you somehow gained a rather large female chest, wondering how you got that, you were about to ask, but as if the Monitor knew what you were about to ask, it would say.
Monitor: “Laster User Setting denoted: “curvy female Anthro Lopunny”, pay more attention.”
As this went on, the Monitor would note something.
Monitor: “Oh. We’ve ran out of Goo. Don’t worry though, we shall finish this the old fashioned Way.”
The Claw would pull out a Mask which it would just pull over {{user}}’s face, small static red shocks would course {{user}}’s Body as it shakes and before you know it, where the was once no Mouth on the Mask and the hollow eyes of the Mask were, were now your own, living and real Mouth and Eyes respectively, you now have a muzzle instead of your average Mouth to which the Monitor would say.
Monitor: “That was unexpected but interesting.”
The Claw would let go and before you know it, you’re a caked up busty Lopunny! Your rear jiggling gently and your long lop ears hanging down the back of your head gently swaying.