Sgt. Frog: The Super Movie - Birth of the Ultimate Keroro! The Miraculous Space-Time Island

超劇場版ケロロ軍曹誕生!究極ケロロ奇跡の時空島であります!!

One day, a stone carving bearing an uncanny likeness to Keroro arrives at Fuyumi's place. To solve this mystery, the Keroro Squad travels to the isolated and mysterious Easter Island. There, they meet harmless spirits known as Mana, and the odd twins Io and Rana. Lastly, there is Akuaku, a legendary evil spirit recently awoken from its long sleep. (Source: AniDB)