  Nowadays human interactions largely take place on social networks, with
online users' behavior often falling into a few general typologies or "social
roles". Among these, opinion leaders are of crucial importance as they have the
ability to spread an idea or opinion on a large scale across the network, with
possible tangible consequences in the real world. In this work we extract and
characterize the different social roles of users within the Reddit
WallStreetBets community, around the time of the GameStop short squeeze of
January 2021 -- when a handful of committed users led the whole community to
engage in a large and risky financial operation. We identify the profiles of
both average users and of relevant outliers, including opinion leaders, using
an iterative, semi-supervised classification algorithm, which allows us to
discern the characteristics needed to play a particular social role. The key
features of opinion leaders are large risky investments and constant updates on
a single stock, which allowed them to attract a large following and, in the
case of GameStop, ignite the interest of the community. Finally, we observe a
substantial change in the behavior and attitude of users after the short
squeeze event: no new opinion leaders are found and the community becomes less
focused on investments. Overall, this work sheds light on the users' roles and
dynamics that led to the GameStop short squeeze, while also suggesting why
WallStreetBets no longer wielded such large influence on financial markets, in
the aftermath of this event.
