Traders bought a slew of bullish contracts on video-game retailer GameStop Corp. over the past two days, less than a month after an X post from Keith Gill, the online persona known as Roaring Kitty, sent meme stocks flying.

From late Monday through Tuesday, more than 100,000 $125 calls expiring Jan. 17 changed hands. Shares have risen almost 12% this week, closing at $31.26 on Tuesday. But they would have to roughly quadruple over the next month for the options to be in the money. Of course, a steep rally would also be enough to boost the value of the options, bought at an average of about $0.795 each.

Call volume rose Tuesday to the highest since Dec. 5, when Gill posted a mock-up of a Time magazine cover, featuring a blank computer screen with a media player that resembles YouTube. Speculation on the meaning of the post also boosted shares of Unity Software Inc. and Clear Secure Inc. that day.

Open interest in the $125 call contract rose by almost 50,000 lots Monday, signaling that the options buying added to positions. 

While implied volatility on the far-off January calls rose Monday afternoon and early Tuesday, it retreated Tuesday afternoon. That signaled possible selling by traders willing to risk a rally and collect premium for the low probability of the options ending in the money. Even as shares rose Tuesday, the value of the option fell by 22 cents.