After a cryptic post from Keith Gill, known online as Roaring Kitty, shares of GameStop (NYSE:GME) and AMC Entertainment (NYSE:AMC) popped on Thursday.

Shares of the videogame retailer jumped as much as 14%, but paired most of their gains to end the day up at 5.9%. The theater chain also paired some of its gains, closing higher at 5.9%.

Gill gained popularity during the January 2021 meme stock craze after igniting a frenzy of activity in GameStop (GME) shares. Known for a cult following among some retail investors, he uses social media platforms like YouTube and Reddit to disclose his trading positions.

However, GameStop (GME) ended flat for the week and AMC (AMC) ended down. And this came at a time that Goldman says should be the height of retail trading, with people on vacation, with a spike in way-out-of-the-money calls lately.

"I don’t think Roaring Kitty has any edge in GameStop, and his last big proclamation was 'I believe in management,'" said Wedbush analyst Michael Pachter. "They’ve done nothing since, and the enthusiasm is definitely more muted than the last time."

GameStop (GME) is scheduled to release its third quarter earnings report this week, with loss per share of $0.03 on revenues of $887.68 million.

GameStop (GME) shares have risen nearly 66% so far this year, beating the S&P 500's gain of about 28%.