Totsuzen! Neko no Kuni Banipal Witt

Fifth-grader, Toriyasu, and his little sister, Meeko, have a dog named Papadoll who has been missing for the past week. One night, two cats take the two children to the distant cat land of Banipal Witt, where Papadoll was abducted. Because of his long exposure to Banipal Witt's sun, Papadoll mutated into a giant dog monster, terrorizing the city under the control of the evil Princess Buburina, who has the curse of turning anyone she touches into balloons. Toriyasu, Meeko, and the cats have until the next sunrise to turn Papadoll and the ballooned citizens of Banipal Witt back to normal and return to their home planet—or end up with the same fate as their dog.

(Source: AniDB)