One of my players started kicking around the idea of a mage who can only cast magic while holding her 'magic' teddy bear, the source of her power. Obviously, this is just a psychological belief, but i was wondering how to GM it, aside from random house-rulings?

Fetish-limited spells. Geas to the Teddy.

It'd be an interesting shaman totem. Plushie.

Now there's a scary thought: Catgirl shaman.

Eh?

Combination of SURGE and a cat shaman. Cat ears, prehensile tail, and as little clothing as possible. Enough to drive any SR/anime fanboy crazy.

bleah. i like SR and anime, but catgirl shamen just drive me into a murderous rage.

Feh. Don't have MiTS.

What about gun-bunnies, mfb? =P

The shortcut: +2 to all magical TN's when she doesn't have the teddy. It can be replaced if lost, but requires a bonding ritual, just like for fetishes.

You don't have MitS so this might not be appropriate, but several months ago I was thiking about something very similar, but in a more general case. The board's response was fairly lukewarm so I stopped working on it (Edit: although now that I look at it most of that impression was all in my head I think), but you're more than welcome to cherry-pick any ideas you find there.

First thing to do though is get MitS and look up Geasea. That's pretty much exactly what you need, and the book is just a good idea to have in general anyway, as magic is of such importance in SR.