Gu is a Marines sergeant working alongside Lieutenant Drake. He has curly black hair and a mustache. He hates carrots and tomatoes. He appears for a second time in the G-8 Arc. Being a non-canon character he was seen in the anime standing alongside Vice Admiral Johnathan and other marine officers during the gathering at Marineford preparing for the battle against Whitebeard. This is not in the manga however.
First Appearance: Movie 4

(Source: One Piece Wiki)