Does it feel like 2021 in here?

Wendy's shares are surging another 10% this morning, in what appears to be a short squeeze of the restaurant chain's stock. The premarket rally stands to build on Wendy's 26% jump yesterday.

The moves have all the hallmarks of the kind of short squeeze that made headlines in 2021, when retail investors banded together online to send shares of companies like GameStop and AMC Entertainment soaring-and inflict painful losses on hedge funds that had placed short bets on the stocks. These do-it-yourself investors bought $15 million worth of Wendy's shares on a net basis yesterday, according to data from Vanda Analytics.

To put that in perspective: That's roughly as much as they had bought of the stock from the start of the year through last Friday.

On the other side of the trade are hedge funds and other investors betting against Wendy's. About 29% of the company's float was sold short at the end of May, according to FactSet. Short sellers borrow shares and sell them, hoping to buy them back later at a lower price and pocket the difference. But the stock's sudden surge has likely forced these traders to buy back shares to limit their losses.

The activity, which gained momentum on Reddit's WallStreetBets forum, is the latest sign that animal spirits are still alive and well in markets-even as retail investors' overall U.S. stock-market buying has been unusually subdued in recent months. Still, the frenzies around SpaceX's IPO, and now Wendy's, underscore how the group is still ready to pounce when the right opportunity strikes.