"Bubble Bath!" is one of the Oobi shorts.
Oobi and Kako are taking a bubble bath and playing with floating toys in the tub. Kako gives Oobi a pair of "ears" made of soap bubbles and pretends that he is a rabbit: "Oobi, rabbit." Oobi hops around and laughs. He then covers Kako in some bubbles and says he is a monster: "Kako, monster." Kako spreads out his fingers and makes monster noises. Kako gives Oobi a bubble beard and a bubble mustache and pretends he is a grown-up.
Oobi acts like an adult by raising his head up high and humming in a deep voice. Oobi picks up a towel, washes the bubbles off of Kako with it, and announces "Kako, best friend." Kako is flattered and says "Aww. Oobi, best friend." He takes the towel and scrubs the bubbles off of Oobi. They sigh and look off into the distance as the episode ends.