It will unlock a whole chain of events you didn't see coming. Believe me, it's not as simple as providing the cookie and then walking away. A. leads to B. which leads to C. and when it's all said and done, you'll have made a decent run through the alphabet.
The best thing you can do to protect your own sanity is to simply deny any mouse a cookie. Be firm. Be unequivocal. Just say "No" and thank me later.