GameStop's shares jumped Thursday after a cryptic post from meme stock influencer Keith Gill, who shot to notoriety after his online personas and bullish bets on the video game retailer sparked a trading frenzy among mom-and-pop investors.

Gill posted a picture of a Time magazine cover with a computer screen on social media platform X. Following his post, GameStop's shares spiked, being last up 13% in late afternoon trading.

Known as "Roaring Kitty" on YouTube and "DeepF***ingValue" on Reddit's popular WallStreetBets, Gill was a key figure in the so-called "Reddit rally," in which GameStop stock surged 1,600% at one point in Jan. 2021, crushing hedge funds that had bet against the videogame retailer.

On Thursday, about 300,000 GameStop options contracts had changed hands by 2:14 p.m. (1914 GMT), at about 1.5 times the usual pace, according to data from options analytics firm Trade Alert.

The stock's 30-day implied volatility — how much traders expect the shares to move around over the short term — jumped to a 3-week high of 132%, up from 93% in the previous session, data showed.

Contracts betting on the shares finishing above $30 by Friday were the most actively traded options, with some 32,000 of them traded by late afternoon.

Gill resurfaced on social media earlier in 2024, after a three-year hiatus leading to a deluge of excited messages from his followers, many of whom have likened the social media phenomenon to a David who took on Wall Street's Goliaths and won.

The meme stock rally in 2021 was set off by Gill's posts on WallStreetBets subreddit about the gains he had made on his investments in the highly shorted firm.

The rally spread to other highly shorted stocks including AMC as Reddit users banded together to squeeze bearish hedge funds, costing them billions in losses and drawing scrutiny from U.S. regulators.

The entire episode inspired Craig Gillespie's 2023 movie "Dumb Money."