To get this wait to any of your piñatas get sick, wait a little while until Dastardos gets to your garden, then click the A-button on any Sherbat in your garden then direct it to Dastardos and leave the rest of the job to Sherbat.
You can get a sherbat by trading online, or by getting a sour sherbat to visit your garden (requires garden level 10) and having a Jack 'o Lantern in your garden, when the sherbat eats it, it will transform into a tamed Sherbat.
Sherbat goes / flies to Dastardos and distracts him with a dance.
Ping, achievement unlocked :)