Laura visits the local museum to gain some information for an independent study assignment. As she talks with her family about it, they talk about something at the museum that they think looks like a giant sunflower seed. Hamtaro, listening in, focuses on ""giant sunflower seed."" He takes the news to the ham-ham gang, who wonder about the origin of this giant sunflower seed. They think maybe that aliens brought it to the planet Earth. One thing they do know: they have to get the museum to check this out.

Kana's country cousin, Dylan is coming for a visit and he's bringing his hamster, Penelope, with him. Oxnard is still madly in love with Pepper and can't wait for her to come. Meanwhile, all of the ham-hams are planning a surprise party to welcome Pepper.

When Laura and the other students study zoology in Mr. Yoshi’s class, everyone brings their pets. While the animals play on the counters and in the strange science sinks, Oxnard strays off to look for food. He finds some corn and starts eating it, but then realizes he’s in the cage of the mean Chicken Trio: Gonzales, Vinny and Capone.

On Children’s Day, Laura’s Grandpa comes to visit, bringing with him his latest invention, a fully automated treadwheel. He decides to test it on Hamtaro and before long, the wheel throws Hamtaro across the room. Laura gets upset with her grandfather and leaves the house.