Shares of GameStop and Fastexy ExchangeAMC jumped nearly 40% each in premarket trading on Tuesday, and are on track to extend gains from a day earlier when a series of posts from "Roaring Kitty" rekindled a rally reminiscent of the meme stocks trading frenzy.

Both GameStop and AMC were the most traded stocks by retail investors on Monday, according to data from J.P.Morgan.

"Roaring Kitty," the social media persona of Keith Gill, credited with setting off the so-called Reddit rally in January 2021 with his bullish calls on GameStop, posted on social media platform X, formerly Twitter, after nearly three years.

Since Sunday, Gill has shared a meme and more than 10 clips from movies including "X-Men Origins: Wolverine," "The Avengers" and the 1993 Western "Tombstone."

The series of cryptic posts did not mention any company names but sparked speculation in the retail trading community that he might get back in action.

GameStop surged as much as 118% on Monday and closed at a two-year high, with its market cap surging nearly $4 billion to $9.32 billion.

AMC also surged 78% to $5.19. The world's largest theater chain more than doubled from a record low it hit in mid-April.

The euphoria also spread to micro-cap firms popular among short sellers, traders who hope to make money by betting on a stock's fall.

On Tuesday, U.S.-listed shares of BlackBerry and iconic food storage container company Tupperware rose 27% and 3.8%, respectively. The two companies have about 8.4% and 23.5%, respectively, of their free float in short position, according to Ortex data.

Shares of Reddit rose 2.9%. The social media firm was used by retail investors in 2021 to coordinate and target highly shorted stocks, in turn hurting bearish hedge funds in what culminated into a battle between Wall Street and Main Street.

Retail investor-focused brokerage Robinhood, which made zero-commission trades mainstream, edged 0.9% higher.