This is a nice way of calming down a group of children as it tests not only their powers of observation but also their ability to listen closely. It can be varied for all age groups.
You will need a recording device such as a smartphone. In an area where they can not be overheard, each child records a sentence describing him or herself, for example: I am five years old, have blond hair and am wearing black shoes. Who am I? When the tape is played back the children must then try to guess who is speaking.
For younger children, an adult can take each child aside in advance and prompt them with the same set of questions.
This can be made more difficult for older children by asking them to say something that others may not know (or be able to see) for example: I have a rabbit named Thumper and like to go cycling at the weekends. Who am I?"
Or, for a group that knows one another better, ask them to try and disguise their voice. Can they fool anyone?