It is absolutely no problem to start crappie in a pond. Catch a few crappie somewhere else and pitch them into your pond...that is it. They are very prolific and will multiply in a couple of years to the point they become stunted. They will be 6--8 inches long and you can read the newspaper thru them.
For this reason the fish people do not recommed crappie in small ponds.
This hasn't been the case in my father's pond (about 1 1/2 acres). There used to be quite a few crappie in there, including a couple slightly over 2lbs. We rarely catch them anymore. There are a lot more bass now.