This improv game is in the following improv game categories:
The top player starts moving about the room (perhaps use music to guide the players). The second line follows the first player, and mimics her movements, and the third line follows the second line. The top player can alternate however she wants (and can be guided with e.g. a change in the music).
The top player can even turn around, and face the second line. Confusion will be complete. Other variations can happen when the top player bumps into the last line, and takes over their movements. See also Aerobics