GameStop stock skyrocketed more than 40% on Thursday afternoon after the meme stock booster known by his online persona “Roaring Kitty” scheduled a livestream on YouTube for Friday.

Roaring Kitty, whose real name is Keith Gill, is an investor and social media personality who has kicked off a renewed meme stock frenzy around GameStop stock in recent weeks.

Gill will hold a live chat about his GameStop stake at noon on Friday. When he last went live in 2020 to tout the investment strategy behind his favorite brick-and-mortar video game retailer, it led to a massive rise in GameStop shares and other meme stocks. That hit hedge funds who had bet against the stock hard before the rally fizzled out. (Meme stocks refer to shares of companies that are wildly popular online — mainly thanks to chatter on Reddit forums and TikTok — and are traded feverishly by retail investors, sending prices soaring regardless of the company’s actual operating results or prospects.)

Following the announcement of Gill’s coming livestream, GameStop stock surged more than 40% to about $44 per share, before giving up some of those gains to trade up 30% on the day late in the afternoon, $41 per share. Trading was temporarily halted because of the volatility.

Gill, who goes by DeepF———Value on Reddit, gained national attention during the COVID-19 pandemic for his bullish analysis of GameStop on Reddit, and drove the first short-squeeze of the video game retailer’s stock in early 2021, which saw its shares surge more than 1,000% in a matter of weeks.

After a three-year gap, he returned to social media last month by posting a picture on X showing a gamer leaning forward in the chair, indicating intense focus. This prompted speculation among followers that he’d return to Reddit and sparked a fresh meme stock rally.

—Rocio Fabbro contributed to this article.