Buying a car as a present

[dcasper70]

So this summer, my wife hinted at wanting a new car. Financially, this isn't a problem, but instead I took her car to a mechanic buddy and he fixed it up enough to get through the winter with ease. So now she's off the new car kick, and fully prepared to ride it out until next fall when the 2007's come out.

While watching Turkey Day football, I saw the standard xmas car ad with the wife opening the jewelery box, seeing a car key, running out to new car with a bow on it. You all know the one...
Well, it got me thinking, which in itself is a very dangerous thing, about buying one for her birthday/Xmas (birthday is 12/18).
We'll be buying one within a year anyways.
I'd prefer to have her in a more reliable car for the New England winters.
I love doing this type of stuff.
She'll blow me for a month straight.

So before any of you try to talk me out of it, don't bother, I'm 85% sure I'm going to do it. My post is more about planning and logistics with questions for any of you current or former car salesmen.

Can I buy a car, and have her as the primary owner, without her signing any documents?
For this to be done right, I'll somehow need to swap out her old car trade-in with the new car on Xmas eve. Are dealerships usually accomodating to this type of thing?
Has anyone got any first hand knowledge of this being done before?

And where the hell can I get one of those big bows?

Any other pertinent info would be appreciated, good or bad.