I'm assuming you have a really, really big slow cooker, and mean to cook a really small turkey?
I've cooked whole chickens in the crockpot, not turkeys, but as long as the relative size of bird and pot permit it's certainly possible. Keep in mind that a slow-cooker is always moist cooking without evaporation -- if you start out with no liquid in the pot, you'll end up with a fair bit of liquid anyway (use it to make gravy!), and the skin is going to end up soft, flabby and nasty-looking. There's no way to get it crisp and pretty in a slow cooker, don't even try.
A couple more points:
1) For food safety reasons I would be even more reluctant to stuff a bird to cook in a slow-cooker than an oven bird. Slow cookers are named so for a reason, and stuffing inside the bird is liable to cook up a good batch of bacteriological nasties. You'd be much safer cooking the stuffing separately.
2) White meat is prone to drying out badly in a slow cooker. Boneless skinless chicken breasts are pretty much impossible to cook in one, unless you like them dried out and rubbery. Whole chickens fare a little better, but not perfectly (some people find the white meat unpalatable even then, or good only as pulled-chicken drenched in sauce). Turkey breasts tend to be on the dry side at the best of times. Given that a slow-cooker turkey can never be a visual treat (pale, flabby skin!), you my want to consider cooking up a bunch of dark-meat turkey parts instead of a whole bird. Dark meat loves slow cookers.