Meet the new meme stocks? Shares of Avis and Bed Bath & Beyond soar.

Shares of the rental car company Avis Budget Group more than doubled on Tuesday, in a sudden and unexpected surge that recalled earlier trading manias in GameStop, AMC Entertainment and other so-called meme stocks. Bed Bath & Beyond, the retailer that attracted some interest during previous meme-stock episodes, also rose sharply in late trading.

The moves appeared linked to several factors, including positive corporate announcements, a surge in interest from retail investors and the squeezing of short sellers. Avis released better-than-expected earnings on Tuesday and executives hinted at plans to buy more electric cars. Bed Bath & Beyond announced a partnership with the grocery chain Kroger and updates about its stock buyback program.

More pertinently, perhaps, both companies are popular targets of short sellers, which also makes them appealing for “meme-stock” traders — who get their name because they share ideas, team up and encourage each other on social media, adopting the inscrutable, joke-laden language of viral internet trends. In a short squeeze, a rising price can force investors who had bet against a stock to buy the shares in order to close their positions, multiplying gains.

This year, the mostly amateur investors banded together to pump up the prices of a handful of companies, gaining a self-fulfilling momentum and transforming the firms’ fortunes. Caught off guard by the hyperbolic trading patterns, Congress has held hearings and regulators have issued reports about what to do, if anything, about this powerful new force in the markets.

Shares in Avis opened about 12 percent lower on Wednesday, retaining most of the previous day’s rise, while Bed Bath & Beyond rose more than 50 percent.