Shares of GameStop (GME) and other meme stocks rose sharply on Thursday after Roaring Kitty, the online alias of meme stock ringleader Keith Gill, posted on X for the first time since September.

Shares of GameStop rose as much as 14% on Thursday afternoon, while AMC Entertainment (AMC), another favorite among meme stock traders, rose as much as 13%. Shares of online pet retailer Chewy (CHWY), also a meme stock favorite, were unaffected.

Gill posted a photo of a fake TIME Magazine cover at 1:45 p.m. ET on Thursday, showing only a desktop computer monitor and keyboard. As of 3:45 p.m., the post had been viewed 3.1 million times.

Gill has repeatedly sparked meme stock rallies by posting cryptic messages and images on X, where he has 1.6 million followers. The latest excitement came in early September, when he posted a photo that was seen by some as a sign that he had sold some of his sizable position in Chewy. That post sent Chewy stock plummeting and GameStop soaring.

After becoming one of the faces of the 2021 meme stock trend, Gill took a long break from public life. He returned to

GameStop and AMC gave back their gains later in Thursday’s session. They were up 6% and 5%, respectively, as of 3:45 p.m. ET.