"Prince Oobi!" (also known as "Prince!") is one of the Oobi shorts.
Uma is at the playground, building a sand castle in the sandbox. Oobi and Grampu walk over to see her creation and compliment it. After putting some finishing touches on the sand castle and patting it down, Uma takes a plastic crown and gives it to Grampu. She names him the king of the castle.
Next, Uma takes a plastic ring, gives it to Oobi, and names him the prince of the castle. Oobi and Grampu wonder what Uma should pretend to be. She doesn't want to be a princess or a queen, so she takes a yellow construction hat and says that she will just be the castle builder. Oobi and Grampu laugh as she pats down her castle again.