The protagonist and first-person narrator of Hunter Thompson's Fear and Loathing in Las Vegas is Raoul Duke (Dr. Duke). In some ways, he is an alter-ego or exaggerated self-portrait of the author Hunter Thompson and the story a sort of roman a clef giving an insiders view of the culture of journalism surrounding the Rolling Stone.
The "sidekick" figure is Dr. Gonzo, Duke's 300 lb. Samoan attorney, distantly based on the actual Chicano activist Oscar Zeta Acosta with whom Thompson really did make two trips to Vegas.
The hitchhiker serves mainly as a device that allows Duke to narrate the back story of the novel.
Lacerda, the photographer, sustains the thin thread of narrative about the journalistic assignment.
Lucy is a quasi-love interest and key to a sub-plot involving legal troubles.