Webtoons—a portmanteau term merging “web” and “cartoons”—are a key energizer of Korea’s ever-expanding popular culture wave, and a signifi- cant content sector in the global online and mobile media/entertainment plat- form environment. To enlarge our understanding of this rapidly transforming arena, this chapter investigates a developing model of collaborative activity between webtoon (and web comic) agencies, producers, and platforms in Korea and China, thus demonstrating its great potential as a new global screen media. First, it defines webtoons and their transmedia nature, and briefly traces their history from the 2000s. Second, it analyzes some of the defining moments in the 2010s, when webtoons reached the shores of China through various types of international collaboration and co-ventures. Finally, a snapshot of Korean company MoonWatcher and some of its recent projects shows how webtoons are forming the basis for a “One Source Multi-Use” IP engine designed to spawn various related media products and formats.