The first thing you feel is the same warm feeling you're used to from all the experiments, so you figure you must be doing something right.
However, it quickly gets much more intense, a bit like when the ray gun got turned all the way up, but across your whole body.
It then gets joined by a constant feeling of mild pressure across your whole body, almost like you're wearing clothes that are a few sizes too small for you, but who's ever heard of clothes that fit and cover a fox' ears or tail?
You're a bit concerned nonetheless, and while both feelings subside after a few seconds, and turn into a rushing sensation instead, the surprised exclamations of Dave and Roy tell you that things didn't seem to go as they expected - you didn't feel your head hit the ceiling though, so you probably didn't manage to grow an excessive amount, so you open your eyes slowly, and the first thing you see is the big sensor tool that Roy just used, or rather, the small cloud of smoke that rises from it.
Safe to say, you definitely managed to do something, and it seems to have shorted out the tool - hopefully Roy added fuses to it, otherwise he'd probably have to go hunting for spare parts.
Speaking of Roy, the techie is now back to being a lab coat wearing mouse person, just like after you first zapped him on accident, and he's already assessing the damage, while Dave is nowhere to be seen.
You stand up, intending to help him out, but stop once you're standing - your point of view has shifted back down significantly, you're definitely a lot smaller than the 6'10" you just were, but it seems like you've shrunk even past your previous size - not exactly ideal, but you definitely won't have to worry about finding fitting clothes now.
Moving also feels a bit odd - you don't feel quite as flexible and graceful any more, and instead there's a certain weightiness to your movements that wasn't there before.
A quick self-inspection shows that you still look mostly the same, so whatever it is about your new body that caused these changes, it doesn't seem to be obvious - you don't check yourself out too thoroughly though, as you wanted to help out with the damage you've caused.
As you come closer, Roy barely looks up while he keeps fiddling with the device. "No worries, it's just a few burnt fuses and molten cables, I'll have that fixed in no time - you might want to help Dave out instead, he seems to have run into some issues."
"Sure, where is he right now?"
Roy points past you, and you turn around to see a humanoid grey tabby cat wearing a slightly altered version of Dave's current outfit - you're pretty sure the original didn't have any extra considerations for tails or animal ears at the very least.
More importantly though, he somehow seems to have made it most of the way up the wall, where he now sits on one of the bigger sensor installations that barely has enough space for him to do so, looking down in apprehension.
"Hey Dave, you doing alright up there?"
He looks over at you and meekly says "No, not really - I know I should be able to jump down there without any issues - cats do harder jumps all the time - but no matter what I tell myself, even looking down there -" he motions straight below him - "is terrifying, let alone jumping."
"Hm, you think you could tell me where the ladders are in this place, or at least something soft to cushion your fall?"
"Ladders, yes, but no idea on the other option - go check out the 'Tech' room, you know the one, there's usually a ladder somewhere in there just so you can reach the upper levels of the shelves."
You nod and run over to grab a ladder.
On the way there, you notice that you definitely feel slower, but can't tell if that's only because your legs are shorter now, but you also have no issues holding the ladder in one hand when you go to close the door - you're definitely stronger than before!
Back in the new testing room, Roy seems to be done fixing the portable sensor device, while Dave is still stuck up the wall, so you quickly bring the ladder over to him and lean it against the wall.
He tentatively puts a foot on the ladder, and slowly steps over, and as soon as he's safely standing on the ladder, he climbs down in record speed, even jumping the rest of the way once he's only three rungs above the ground.
"Thanks a bunch, I'll go put the ladder back now. Oh, and please don't tell anyone that I got stuck like that, I can already hear the other guys calling me a 'scaredy-cat' if they ever find out."
"Sure, I guess that's part of your new animal instincts then?"
"Whatever, it was, it sucked.", and with these words, Dave grabs the ladder and exits the building.
Roy, on the other hand, comes up to you and starts talking excitedly. "That was quite the discharge you caused back there - bright, and powerful!
No idea about specifics, unfortunately the high-fidelity sensor machine got fried before it could log any usable data, so all we have is some rough estimates based on the regular sensors across the room - minus the one Dave jumped onto, I suppose.
Speaking of which, we'll have to go over the whole setup to see if everything still works, so we can't even test our new bodies properly.
Good thing it's already time for lunch - we'll give everything a once-over right now and fix the rest in afterward.
In the meantime, feel free to spend your time however you want, but in the interest of accurate data, I'd ask you to avoid any additional vectors of change for the time being - a tough ask at this event, so try to keep it at a minimum, or at least report if you feel like you interacted with something of that nature. We should be done in a few hours though, so it won't be too long until we can continue."