Michael Ritter was leading a staff meeting in Los Angeles last fall when his phone buzzed with a group text from a teammate in the football videogame “Madden NFL Mobile.” It was one of nearly a dozen messages that day pleading for Mr. Ritter to get his head in the game.

“Why aren’t these people working?” Mr. Ritter, a 34-year-old technology executive, recalled thinking about his teammates.

The answer came when one of them suggested Mr. Ritter play between classes like everybody else. “It definitely made me feel old,” he said.

Videogame players join virtual teams often with people they don’t know, just like in real-life pickup games. Unlike the park or playground, though, online teammates usually know little about each other, not even real names.

When older and younger gamers join forces, things can get awkward. Micah Gantman, a 33-year-old mobile ad-tech executive in New York, said he spent $200 to $300 a month to upgrade his army in the game “Clash of Clans,” where goblins and mustachioed barbarians raid enemy villages.