Jack (ジャック) is a little pirate boy that Nobita befriended. He is Betty's little brother that disappeared along with their father on a voyage to the Treasure Island. He is shown in the 1998 movie, Nobita's South Sea Adventure.
Sometime before the events of the movie, Jack along with his father Captain Cole and the crew sailed to the Tomos Island to search for the buried treasure. His father told him to stay behind and look after the ship which Jack did so. However, the crew never returned from the treasure hunt and shortly after, their ship disappeared. This event stranded Jack alone on the island and worried his sister Betty. Jack had to live on the island by himself using his own survival skills.
Several weeks later, Jack discovers a stranded Nobita on the island beach. Though he is hostile toward Nobita at first, Jack quickly comes to understand that Nobita is harmless.
- Interestingly, Jack is technically the first person to call Nobita "Noby", a name that would later be used for his English Dub name. This was not retained in Disney XD Asia dub, however, due to the lack of language barrier unlike in the original version.