"Sleepover!" is an episode of Oobi from the first season.
Oobi goes to Kako's house for a sleepover. Uma misses Oobi terribly. Grampu does his best to make Uma feel better, but the only thing that works is a phone call and a lullaby from her big brother, Oobi. — ABC Television
Oobi and Uma pretend to have a conversation over the telephone when it begins to ring. Grampu picks it up and tells Oobi that someone is calling for him. Oobi takes it and hears Kako, who invites Oobi to his house for a sleepover. Grampu okays this and Oobi goes to pack his things for the night. Uma asks Grampu what a sleepover is. He explains that Oobi will sleep at Kako’s house. Uma is excited, as she believes that she will visit Kako as well. Grampu tells her that only the boys will be there, disappointing her. Grampu tries to cheer Uma up by creating a sleepover at their house, but she is still depressed. "Nice try," she tells him as she sulks.
As Oobi is about to leave, Uma puts a photograph of her in his suitcase. She asks if he will remember her. Oobi assures her that he will and closes the suitcase. He explains that he will be back the next morning and is interrupted when Uma hugs him and refuses to let go. He says “goodbye” to her and leaves. Later, Uma decides to have a tea party by herself. She takes a sip from her teacup and invites the viewers to join her tea party. Grampu walks in and joins as well. Uma asks him to act like Oobi. He plays along and shifts his fingers to look like Oobi’s, with some minor difficulty. Uma later asks "Oobi" to play dress-up with her. The next scene shows them wearing hats and purple veils, speaking in posh British accents. They drink their tea, seeming to have a good time, but Uma is then reminded of Oobi's sleepover and becomes very depressed.
Grampu leaves her alone as she walks to her room. She cries about Oobi until Grampu walks in with the telephone. Oobi is on the other line, talking about how he misses Uma as much as she misses him. He reassures her that he will return the next morning. Oobi sings her the "Uma Sleep" song and she falls asleep immediately. Grampu comes in and congratulates him on doing a good job of calming down Uma. In the next scene, Kako asks the viewers if they have any siblings. Afterwards, Oobi and Kako are playing with stuffed animals when Mamu tells them to go to sleep. Oobi gets the idea to play a letter game with Kako, using words that start with the letter S. They go to sleep as the episode ends.