Anonymous commenting is on, if you don't have an LJ account or are just feeling shy.
All South Park-related wishes are totally cool, including canon, AU, RPS, crossovers, and fusions. If you can dream it, you can wish it -- go for it, dude!
There is no limit to how many things you can include in your wishlist (though there's also no guarantee you'll get them).
Having said all that, keep in mind that this is really meant as a place to give and receive little treats. So you can make a long, complicated, specific request if you want, but if you include some general things as well, you'll have a better chance of getting some treats you'll be into.
(Additional details on how this event works are here; contact info is here.)
We'll be hanging up stockings until December 10th, and you can sign up anytime between now and then using this form: