"Owww!"
You groan, pressing a hoof to your forehead in a futile attempt to stem the pain. You're not too badly hurt, in fact your hind legs are fine, although your muzzle feels like you just got hoofed in the face by Snowflake, since it took the brunt of the impact. The pain fades relatively quickly, but it still hurts to know that Derpy does things like this all the time. You shudder, it feels really weird thinking about the pony who is essentially YOU in the third person like that. What if you can't prove you're actually human? You are just a little pony.
Just a little pony...
"No!"
You shout to yourself, sniffling slightly and mentally scolding yourself for being so negative. If you want to get anywhere like this, you'll have to avoid having any more nervous breakdowns. Shakily, you angle your front hooves level with the floor and press down, lifting your head off the ground and raising your neck, the new definition of 'up' confusing you for a moment. "You can do it, Derpy." You whisper reassuringly to yourself, before pressing downward with your hind legs, lifting your rear end off the ground and standing up fully for the first time in your new pony body. It's a small accomplishment, but you're proud of it nonetheless.
That smile soon fades as you realise you just referred to yourself as Derpy. Ugh, why did your brain have to change along with your body? Come to think of it, what IS your name? You think for a moment, tilting your head and staring (approximately) up at the ceiling. No matter how hard you try, the only name you can ever remember having is Derpy. You know you had a different name when you were human, but it's simply not there, as if all memory of it had simply been wiped from your memory. You don't want to think too hard about what else has been changed in your mind, but you've definitely been thinking with ponyisms since waking up, and there's always that small problem that you've been turned into a BUCKING CARTOON CHARACTER. Whoever did this to you is going to get a hoof to the face.
Turning back to the task at hoof, you raise a foreleg in preparation to step forward, the opposite leg lifting automatically to keep yourself balanced. It's an odd feeling, but it comes surprisingly easily to you, as if you've been walking this way your whole life. You rock forward on your remaining two legs, allowing your foreleg to make contact with the ground once again before taking another tentative step forwards.
"Ugh, this is taking forever!"
You groan, your empty stomach rumbling in agreement. Ah, yes. Food! Satisfied that you can balance on all fours properly, you begin to slowly and carefully trot in a circle around you room. It feels a lot like walking on your hands and knees, only your legs aren't dragging along the floor and it actually feels comfortable this way. Now that you're confident you won't be tripping over your own hooves, you stumble clumsily over to the door. You bend your forelegs together and jump upwards, catching the door handle in your teeth and pulling downwards. After a bit more stumbling to walk backwards on your hind legs, the door swings open and you drop back down onto all fours with a thud. You make a mental note to leave all the doors open in your house from now on, those handles are clearly not designed for ponies.
You trot cautiously into the landing, your head swinging from side to side as you settle on where to go next. You're in dire need of a muffin, but you need to take a good look at yourself first. You canter over to the bathroom, the door thankfully swinging open at a nudge from your muzzle. You approach the sink and repeat what you did with the door, latching onto the edge of the sink your forelegs and hoisting yourself up. You look expectantly up to the mirror placed above the sink and, sure enough, the spitting image of Derpy stares straight back at you. It takes a little effort, but you manage to get your eyes to both look in the same direction and properly focus on your face. (http://i.imgur.com/KOhQ6cU.png)
You giggle softly to yourself in that weird, high-pitched voice as you make all the expressions you remember from the show. You scrunch up your nose and turn your head to the side, allowing your eyes to drift apart again in a perfect imitation of the 'Derpy scrunchy face'. You flop your ears about playfully, in the same way you would have moved your eyebrows as a human. It looks quite silly, but at the same time it's also kind of cute, those two furry triangles twisting to catch every sound available to them. You can hear the traffic outside, the birds fluttering between the trees, and the people walking down your driveway, even from way up here and through a window.
Wait, people coming down your driveway?
Oh. Crap.