This trick requires some patience and a good amount of money. Having the Miracle Gloves also is recommended. Call up either of the livestock farms and buy as much fodder/feed as you can afford, usually in amounts of 99 each. Sell all of them, which is easy with the Miracle Gloves equipped. The Sprites require the following numbers to be unlocked. Note: All the sprites unlocked are part of the harvest team.

Paddy: About 500 items sold.
Fraw: About 1000 items sold.
Ridge: About 5000 items sold.
Ali: About 10,000 items sold.
Cady: About 30,000 items sold.