Wario Land II, known as Wario Land 2: Nusumareta Zaihō (ワリオランド2 盗まれた財宝, Wario Rando Tsū Nusumareta Zaihō?, lit. "Wario Land 2: The Stolen Treasure") in Japan, is a video game released for the Game Boy in 1998. It was the last first-party title made for the Game Boy and was later remade to take advantage of the Game Boy Color hardware. In this game, Wario has to recover his treasure from Captain Syrup and her Black Sugar Gang (formerly the Brown Sugar Pirates).
Source: Wikipedia, "Warioland II", available under the CC-BY-SA License.