‘Roaring Kitty’ Came Back, Chugging Beer and Talking GameStop. Shares Plunged.

Around lunchtime Friday, on a YouTube livestream watched by half a million people, a bandanna-clad man in white sunglasses grinned into his webcam and teased: “I’m about to show it.”

Oh, stop it. He meant his brokerage account.

Keith Gill, the man better known as Roaring Kitty, who became one of Wall Street’s unlikeliest celebrities during the meme stock mania of 2021 before disappearing from public view, was onscreen — and in his signature fashion, mixing beer, comedy and market commentary.

A quick refresher: Three years ago, Mr. Gill’s unrestrained cheerleading of GameStop and other companies on social media made him a kind of rabbi to thousands of day traders stuck at home during the pandemic — people who bought loads of shares and drove those stock prices to nosebleed levels. These traders’ use of internet memes and social platforms like Reddit to trade stock tips ushered in a new class of investors.

Mr. Gill, 37, whose renown was such that he testified for Congress and inspired a film, “Dumb Money,” had been out of the spotlight for the better part of three years, having come under some regulatory scrutiny. He vaulted back into prominence last month by posting on X a cryptic illustration that many took as a sign that he had returned to day trading.

That post was followed by more cryptic social media messages and the leak on Reddit of a screenshot showing that Mr. Gill held more than $100 million of stock and options betting on GameStop. Its shares immediately soared — “to the moon,” in meme speak. The videogame retailer used the opportunity to sell new shares, raising more than $900 million.

Thus, anticipation was high when Mr. Gill’s dormant YouTube account on Thursday carried an announcement that he would host a noon stream the next day. CNBC put talking heads on the air to speculate on what he might say. The Wall Street Journal set up a live blog.