A real estate salesman in Valparaiso, Indiana. A former line cook from the Bronx. An evangelical pastor and his wife in Huntington Beach, California. A high school student in the Milwaukee suburbs.

They are among the millions of amateur traders collectively taking on some of Wall Street’s most sophisticated investors — and, for the moment at least, winning. Propelled by a mix of greed and boredom, gleefully determined to teach Wall Street a lesson, and turbocharged by an endless flow of get-rich-quick hype and ideas delivered via social media, these investors have piled into trades around several companies, pushing their stock prices to stratospheric levels.

Some of the names are from an earlier business era. BlackBerry’s shares are up nearly 280% this year. Stock in AMC, the movie theater chain, has surged nearly 840%. But the trade that captures the David-versus-Goliath nature of the moment involves GameStop, the troubled video game retailer that was once a fixture in suburban malls.