Within the world of video game design, the topic of environmental design and storytelling has been the subject of academic discourse for decades. A key component of these game-worlds, which is often mentioned, is the implementation of non-player characters, or NPCs for short. To better understand the process of NPC design from a game-world perspective, this study attempts to compile different design processes, design perspectives, and design frameworks related to NPC design and contextualize these from a game-world perspective. By doing so, the process of creating authentic, immersive, and believable NPCs can be visualized and presented in the form of a unified framework consisting of different NPC design frameworks. To accomplish this, a literature study has been conducted in order to map different key NPC design aspects such as mechanics, visuals and behavior. Video game examples and alternative but related forms of media have also been used to provide credibility and argue for the different frameworks' applicability in game design. From the findings of the study, future research opportunities within thisfield are opened.