Keith Gill, known as 'Roaring Kitty' on Reddit, has made a significant impact on GameStop's stock price by revealing his substantial holdings. Gill disclosed a position worth over $200 million in GameStop shares and call options, including $115.7 million in shares and $65 million in June 21 $20 call options. His portfolio includes 5 million shares and 120,000 call options. His return to social media has driven GameStop's stock price up by as much as 90% in pre-market trading, reaching $39.89. The surge has caused short sellers to incur nearly $1 billion in losses, with $993 million lost since Friday's close. Gill's influence on the market remains strong, with his portfolio potentially reaching $300 million or more. This development has reignited interest in meme stocks, with other related stocks like AMC also seeing gains.