The GameStop case study analyses a real-life event documented in the media, academic research and the cinema about the spectacular and unexpected surge in GameStop's share price in 2021. It illustrates the transformation of retail investment, driven by the intersection between gamification of finance by online applications and social networks, bringing new market players, liabilities by multi-sided platforms and regulatory oversight issues. In this example, a new type of trader is emerging : young, hyper-connected neo-traders placing their orders on 'free' platforms with a design inspired by video games in the specific context of the confinement caused by the Covid-19 pandemic (teleworking, unemployment, free money and cheques distributed by the U.S. government). These neo-traders got their information from a new type of influencer (finfluencers) and coordinated on social networks around a few companies, GameStop in particular, until the traditional financial players, and hedge funds in particular, staggered to their feet, and then watched helplessly as the platforms suspended trading. Accusations of market manipulation, conflicts of interest and even a new Wall Street conspiracy against Main Street retail investors then exploded. This case study can be used in Innovation Management, Information Systems, New Technology Strategy, Finance or Ethics courses. It can be run in various ways, depending on students' level, and a scale is provided for use as an exam subject.