Pokemon first became a cultural phenomenon in the United States in 1998 with a game that let players capture, train and fight the imaginary creatures. In an era before high-speed internet or mobile web access, Nintendo broke new ground by selling cables that let players link their handheld Game Boy devices together to trade or compete with one another. In the past two decades, Nintendo has kept churning out games, cartoons and merchandise, but the franchise had stopped commanding the immense popularity it once held.