"Halloween!" is an episode of Oobi from the second season.
Oobi is shown wearing a homemade dinosaur costume in his room. Uma walks over, wearing a rabbit costume. The siblings have each other guess what their costumes are meant to be. Oobi invites the viewers to guess as well. Grampu appears and admires the children's costumes. He volunteers to take them trick-or-treating with Kako. They walk to Kako's house, where they greet Kako and Papu. Papu gives the children candy. Oobi asks Kako why he is not wearing a costume. Kako unwillingly tells Oobi that he is afraid of trick-or-treating and has never gone before.
Uma tells Kako that she will help him overcome his fear. She takes the tail of her rabbit costume off and places it on Kako's head, telling him that it is a snowball costume. The children and Grampu walk over to Mrs. Johnson's house, where they hope to get candy. Angus appears in a ghost costume along the way. Kako is startled at first, but Uma shows him that it is just a costume and there is nothing to be afraid of.
After they arrive at Mrs. Johnson's house, Uma demonstrates how to ask for a treat. Kako follows her lead and receives a box of raisins from Mrs. Johnson. She tries to guess what his costume is modeled after, but cannot get it right. Kako tells her that it is not a flower or a cotton swab, but a snowball. After each of the children gets a box of raisins, Oobi waves "goodbye" to the viewers and the episode ends.