The disclosed technology is directed towards inserting user-personalized or other user-related supplementary media content into primary media content being presented to the user. The personalized media content can be inserted into available insertion slots associated with the primary media content. The inserted content is based on the context of the primary media, e.g., a location or theme of a movie scene. For example, upon obtaining primary media content that is video, supplementary media content related to a group of frames of the primary media content can be determined. Supplementary media content is combined with the primary media content at a presentation position associated with the group of frames to output modified media content. For a video, for example, the supplementary content can be inserted between scenes, overlaid onto a scene, or presented proximate a scene.