The feeling doesn't start out unpleasant.  In fact, if anything, it's barely noticable as you're sitting at your computer.  A bit of tingling in your legs, but hey, you've been sitting down for three hours, they might be getting a bit restless.  Nothing really to worry about on that scale.  A little bit of leg twitching is fine and good for them as you sit there.  A bit of scratchiness as your jeans run along the legs is similarly ignored offhand as you're busy with other things, until one of your socks slips right off your foot.  *THAT* gets your attention.

Excusing yourself from your current activities, you take a peek down, since htose socks weren't that loose, and see something rather...different.  Your foot seems to be compressing, reforming.  Toes have shortened and drawn into the main mass, although they're still defined.  The entire structure has lengthened, seeming to leave you walking on your tiptoes.  Small pads are coming in on the base of what now seems to be your foot, and the nail is darkening and compressing into what seems to be a digging claw.

Hobbling to the bathroom on one unfamiliar leg proves a bit of a challenge, but it's probably best to get to a mirror.  Lifting the leg on your pants once you arrive shows that the hairs on your leg are standing on end, and have to have multipled tenfold since you put the jeans on this morning.  They're still dividing and thickening, forming what almost looks like a pelt across your legs as you examine.  A quick brush across with your hands quickly indicates this IS a part of your body, based on nervous feedback.  The leg structure itself seems to be adjusting a bit, being a bit longer and more spindly, but the sensation itself isn't at all painful...it just is odd to watch.

You're snapped out of examining the legs and your now almost fully altered feet by the feeling of SOMETHING starting to invade your pantleg.  Its long and developing; as you reach back to free it, your hand wraps around a large bushy tail.  Which'd be odd enough, but your brain is also feeling your hand wrap around the tail, so it's connected to you, although your conscious mind and subconscious seem equally confused about the implications of this.  Standing up to get a better look at it is slightly challenging, given your legs having almost finished changing.  It looks similar to the tails on wolves or large dogs you've seen in the past...but it's attached to you.

Lifting your shirt with one hand, further hair...or fur...is growing in on your stomach as your body starts to alter.  Your belt slips off your changing waist, leaving your jeans hanging loosely against your hips as your stomach furs over and slims down.  Your trunk in general alters, becoming seemingly longer and slimmer, meaning that your shirt hangs oddly off your shoulders, like it's two sizes too large.  Fur covers your chest and stomach as an odd warmth fills your chest.  It isn't unpleasant, just...alien...as your heart rate increases.  The fur itself seems to be altering itself, switching over to a blue color as it grows in.  

Your upper arm has furred as well, and suddenly your lower arm skin dries out and starts cracking like its winter and you haven't been wearing gloves.  But on the backs of the arms it's breaking into clearly defined geometric shapes, and the entire surface is becoming 'pebbly'.  Your fingers lengthen a bit, with the exception of the pinky, which rapidly atrophies away, its mass absorbed into the other fingers.  Dark claws...or talons...grow out of the edges of the fingers as this happens, and the hand itself suddenly feels far more powerful, like once you closed it on something it would never escape.

Your examination of this is broken by a sudden massive itching sensation around your neck.  You've never had to shave much but suddenly it looks in the mirror like you have a gigantic neck beard, as the trademark mane grows out.  It bushes out underneath your upper shirt, filling the collar and top, making for quite an odd sight indeed, although pulling your shirt down a bit quickly fixes that.  Oddly, one of your early thoughts is how completely useless any razor is going to be on this much fur.

Examining further in the mirror, your ears seem to be sliding upwards, a point having developed on top of them.  As the migration continues, they take on a more triangular shape, and start twitching.  You can FEEL there's a seperate part of your brain that controls them now, perking and flattening and rotating your ears as things change.  Your hair darkens to blue as well as your skull grows out into a more triangular vulpine design.  Which should hurt, but doesn't, although the absence of sensation is perhaps even more off-putting.

Your teeth liquify into gelatin as they reform in your mouth, switching from herbivore to vulpid carnivore in the process, and your nose covers the front of your new muzzle, turning black and getting a bit damp.  New sensasations flood in through the nose...bathroom, shower, algae, soap scum, shampoo, bleach, toothpaste, and you seem to be able to identify them without much trouble as it happens.  Your eyes also set back a bit further in your skull and a modicum of color drains from the world slowly as they adjust, an entire chromatic spectrum removed from them as the changes complete, leaving you staring in the mirror and wondering how, and what, just happened.  And why.