Mirror Mimics
Begin the game by gathering all of the students together in a circle. Tell the preschoolers to pair up with a person standing next to them. If one player's left out, place him with another pair so that you have one three-player team. Out of every pair, one player becomes the "leader" and the other player becomes the "reflection." The leader comes up with movements while the reflection mimics those movements as they happen. For instance, if the leader raises his arms, the reflection has to raise his arms at the same time as the leader as seamlessly as possible. Switch the roles among the pairs after five minutes has passed.
Play Pretend
Gather the students in a common area as you stand in front of them. During the game, call out instructions such as "Pretend you're a dog" or "Pretend you're a tree." The students all have to quickly get into the mindset of the thing you've given them. For instance, if you called out "Pretend you're a ballerina," the children might twirl around or try and stand up on their tiptoes. As the game goes on, pick more abstract things like "Pretend you're in love" or "Pretend you're the sunset." The game continues for as long as you want.
Big Chief
Assemble the preschool students into a standing circle. Select one of the players to leave the circle and go to another area so he cannot hear you or the other players. Out of the group, pick another player to "transform" into the "Big Chief." The Chief stands within the circle, as inconspicuously as possible, while he starts movements that the other players follow. For instance, if the Chief hops on one foot, the other players must also hop on one foot. Have the Chief start this process while you go fetch the other player out of earshot. Stand that player in the middle of the circle. He must try and discover the person starting the movements by looking around the circle. Let all of the players take turns guessing, as well as playing the part of Big Chief.