From the Super Mario Wiki
In this minigame, the player has to find one of the four characters (Mario, Luigi, Yoshi, or Wario) amongst a large crowd of the others by tapping whichever of their icons is shown on the wanted poster on the top screen with the stylus. As the player advances, the minigame increases in difficulty, adding more characters, hiding them behind other characters, and even having the icons move. The player starts with ten seconds on the first round, and gains five seconds by tapping the correct character, but loses ten by tapping any other one; the timer has a maximum time limit of fifty seconds at one time. The highest score the player can obtain by clearing the levels is 9999; afterward, the game continues, but the score counter and level number not increase. The minigame ends after the player runs out of time.
 In-game instructions
"It's easy to get lost in a crowd! Find the one who disappeared and touch him. There he is!"