Jimmy is a fictional character who appears in both the 1933 and 2005 versions of the movie King Kong, as well as the 2005 game.
In the 1933 film Jimmy is a sailor aboard the tramp steamer the S.S. Venture. In the 1933 film he is played by an unknown, uncredited actor, and is a relatively minor character that doesn't actually appear until after Ann Darrow's sacrifice to Kong by the natives of Skull Island. He is one of the crew members who volunteer to accompany Jack Driscoll and Carl Denham on their mission to rescue her, and is the man chosen to carry Denham's gas bombs. His name is only mentioned once.
In the 2005 remake, Jimmy is played by Jamie Bell and the role is expanded. He is a lookout on the Venture and a protégé of first mate Ben Hayes whom he views as a father figure. He is much younger and something of a kleptomaniac, introduced stealing Jack Driscoll's pen when he brings him his lunch. After making Jimmy return the pen and chasing him off, Hayes tells Driscoll that Jimmy does not mean any harm, and informs him that he found Jimmy hiding in a cage some years ago, with his arm broken in two places, and "wilder than half the animals in here." Hayes says, further, "He still won't tell me where he came from, but it wasn't any place good." Later, Jimmy reveals that he taught himself how to read by reading Heart of Darkness, which he borrowed on a "long-term loan" - i.e. he probably stole it from a library. In the scene where Kong tries to recapture Ann, Jimmy shoots at Kong with a tommygun but is injured when Kong throws his boat against a boulder. He is seen being held above water by Jack Driscoll.
He also appears in the video game based on the 2005 film. Jimmy appears in the 1932 and 2005 novelizations of both films, by Delos W. Lovelace and Christopher Golden respectively, as well as the 1991 Monster Comics adaptation drawn by Don Simpson. Although Lovelace and Golden's novels have Jimmy relatively similar to his counterpart(s) in both films - that is, young and not very big - Simpson's comic portrays Jimmy as being middle-aged, and quite large and brawny.