Instructions
Go to The Port area and make for the Super Seeds shed to buy plant seeds. If you've never been to The Port or shed before, click "To Super Seeds" in your monster's garden, or click The Port on the world map, and then enter the shed.
Select and buy seed packets. For Rocky, you'll need to buy one Silly Peppers packet, one Love Berries packet and one Crazy Daisy packet. For Liberty, buy three Love Berries packets. For Cleo, buy one Snap Apple packet and two Crazy Daisy packets. For MiniBen, buy three Snap Apple packets.
Travel back to the Moshling Garden and plant three of the seeds you need to get one of the Worldies. If you've never planted Moshling Garden seeds, click the seeds bag, then simply click and drag each packet to a dirt pile.
Leave the garden and don't return for at least six hours. Upon your return, you should see three grown plants. If the correct plants grew, the Moshling you want will walk in front of them: any Hot Silly Peppers, any Love Berries and Pink Crazy Daisy for Rocky; Black, Red and any Love Berries for Liberty; Yellow Snap Apple, Blue Crazy Daisy and Pink Crazy Daisy for Cleo; and three Black Snap Apple for MiniBen.
Agree to keep the first Worldies Moshling when prompted to add it to your monster's Moshling collection.
Continue to grow plants in the garden to collect the rest of the Worldies.