Who is Roaring Kitty and why is he causing a GameStop stock surge?

Shares of GameStop, the embattled video game retailer at the center of the 2021 meme stock frenzy, are surging again after the return of the “Roaring Kitty.”

Roaring Kitty, who is legally known as Keith Gill, kicked off another stock market surge this week with his first post on social media in nearly four years. His return sparked a new flood of interest in shares of GameStop, the stock that launched Gill to fame and fortune, along with others favored by an online community of amateur traders. 

So who is...