Trick stick
From PinataIsland.info, the Viva Piñata wiki
Trouble in Paradise
The trick stick is a tool introduced in Trouble in Paradise used to teach tricks to your piñatas. Each species can learn two unique tricks. To teach tricks, simply feed the Pinata the item needed and when a green circle appears, poke the Pinata with the Trick Stick!
Additional uses
Using the Trick Stick on a cocoon will instantly free the piñata inside. Poking () the cocoon causes the Piñata to stay at its current size permanently. You can poke it before, during, or after the cocoon grows to have a permanently small, medium, or large adult piñata .
Also, Trick number one for all Pinatas involves them doing something themselves, while trick number two always involves them using an object (Which is their attack)