GameStop shares double after tumbling for much of February

Wall Street’s mania over GameStop is on again, at least for one afternoon.

Shares in the troubled video game company more than doubled Wednesday to $91.71 apiece, the stock’s best day since Jan. 27, when it was going for $347.51 a share.

A rally in GameStop has been rare this month. The stock, which soared 1,600% at one point in January, is down nearly 72% so far this month, though it’s still up nearly 387% this year.

Shares in AMC Entertainment, another stock hyped by online social media forums, jumped 18.1%. The movie theater chain’s stock is up nearly 60% this month and about 329% this year.

The sudden, sharp move higher in GameStop and AMC Entertainment left even some members of Reddit’s WallStreetBets forum, which helped cheer the stocks’ meteoric rise last month, scratching their heads.

“Can we honestly sound off on what we think is happening?” wrote one Redditor. “Is there any reason for this 150% spike??” asked another.

GameStop’s wild ride shocked Wall Street, forcing the market to gird for more volatility. It prompted Congress to hold a House hearing last week into what led to the frenzy and whether smaller investors need to be shielded from taking big risks.

Individual investors on Reddit and other social media forums encouraged each other to buy GameStop, AMC Entertainment and select other stocks in a bid to hurt hedge funds that were betting the stocks would lose value. The move, known as a “short squeeze,” can lead traders who were using options to bet against a stock to abandon their bets. To do so, they have to buy shares of the stock, which pushes the price even higher.

GameStop was an extreme example because some of its shares had been sold short multiple times.

Gust Kepler, CEO of stocks and options platform...