Grampu bakes cookies for Oobi, Uma, and Kako. While the kids eat, they do their own impressions of Grampu. They all talk about Grampu and how friendly he is. This inspires them to make a holiday in Grampu's honor called "Grampu Day". To celebrate, they decide to give him a statue, special food, and a present. When Grampu comes back, they wish him a happy Grampu Day, and tell him the plan.
Oobi goes off to make a clay statue, with Grampu posing as the model. While Oobi sculpts the clay, Grampu gets an itch and tries to scratch it. Oobi finishes the model, but to his disappointment, it looks nothing like Grampu. Trying to spare Oobi's feelings, Grampu says he thinks it looks just like him. He awkwardly tries to move into the position of the statue.
Meanwhile, Uma is looking around her room for a present, but all she finds is dirt. Kako is in the kitchen, making Grampu some special food. He thinks about the foods Grampu likes: tuna, which Grampu likes, and jelly, which Grampu loves. He mixes the two things together. He tastes it, but finds something's missing, so he adds hot sauce, which he loves. He gives the food to Grampu, who is excited to try it. However, just one bite makes him gasp for air due to the hot sauce. Grampu tries not to hurt Kako's feelings by saying "Mmm." Kako asks the viewers to do the same as he unknowingly force-feeds Grampu the disgusting food.
Uma's still looking for a present. She walks into the bathroom but only finds a tube of toothpaste. The kids gather in the living room to celebrate, but Uma tells the boys that she had no luck finding a present. Oobi gets an idea and whispers it to Uma. She agrees with his plan and sings a special song to Grampu. The kids hug Grampu, and he thanks them for being so nice.
Later, Oobi and Kako find some leftover clay. Oobi gets the idea to play a guessing game with it. He makes a new statue and asks the viewers to try and guess what it is. It's revealed to be Kako. Afterwards, Oobi and Grampu ask the viewers about their grandparents. A group of preschoolers are shown talking about their families. Oobi and Grampu look at each other happily as the episode ends.