Go! Anpanman: Purun, The Soap Bubble (2007)

Anpanman's friends go see a bubble show performed by Shabondama-hime and her Shabondama Girls, who make exquisite bubbles by playing their flutes. One of the girls, Purun, can't make big bubbles no matter how much she rehearses. She feels inadequate as she goes to retrieve her lost flute, which Creampanda finds and goes to return. Meanwhile Baikinman takes over Shabondama-hime's castle and steals the flutes, using their power to create evil bubbles, and Purun must realize her own importance and save the day with Anpanman's help.

Unfortunately the movie Go! Anpanman: Purun, The Soap Bubble is not yet available on HBO Max.