Kidou Butoden G Gundam: Fukushuu no J Gundam

Domon Kasshu and Rain Mikamura visit Neo Dodo, a picturesque island where a resort hotel run by Mocchi Ohgane and the surrounding town have been attacked by a mysterious Gundam. Domon agrees to look into the matter, only to be overwhelmed by a surprise attack from a skilled boxer, who has an "invisible uppercut" that he isn't able to see. This boxer is revealed to be a talking kangaroo, the Gundam Fighter of Neo Australia who kidnaps Rain before returning in the Jumping Gundam to challenge Domon. (Source: The Gundam Wiki)