Charlie Charlie is the most recent, and most American, incarnation of a rather old game. This form may have first originated as Juego de la Lapicera in Spain, although it is simply another game in the age-old spirit of do-it-yourself séances, à la the Ouija board, dumb cakes, and cartomancy.
While the exact methods vary, the most common version of Charlie Charlie consists of a piece of paper marked in quadrants, labeled yes/no/yes/no, with two pencils laid across to divide the quadrants. One pencil lays flat on the paper, and the other pencil is balanced on top if it crosswise. And, then, or course, you ask the pencils questions.
The upper pencil is unstable enough to rotate ever so slightly under the pressure of a whispered breath, so one finds that the spirits are usually willing to talk. As this is an activity undertaken primarily by tweens and teenagers, the most traditional questions are about which members of the opposite sex are interested in dating, but anything is fair game.
Charlie is generally said to be a Mexican ghost (or demon), but there don't seem to be any clear ties to Mexico (or, dare I say it, ghosts). I suspect the first person to popularize Charlie Charlie on YouTube had a hard time thinking of exotic names, and no one ever bothered to rename the game.
Because internet, the game is oft referred to as the Charlie Charlie Challenge, and if one is interested in learning more, the hashtag #CharlieCharlieChallenge has been around since 2015, and is still trending among impressionable youth.