I've played Farmville for a while, but no. Not that I know of, sorry.
Yarn
Harvest wool
you don't! you just have to adopt them when somebody finds a lost one on their farm.
you can get black sheep on farmville by adopting them. to do this go to your facebook homepage, then on the left there is a bar that has different categories for news feeds, click on farmville. now scroll down until you find a black sheep and hit adopt some people may have already adopted them, but keep trying youll eventually get one
A notice will randomly pop-up while your playing Facebook thwt asks you if you want to adopt a black sheep..... Hit yes.
black bacon :)
you get yarn.
Wool
This is because the Farmville creation team created it like that.
yarn
no. actually
Same way you get everything else in FarmVille. A friend has to fine a lonely black cat on their farm, post it on their wall, then you have to click on it before all of your friends do.