You will need:
2 paper/plastic cups (or any similar shaped container - I'm using small Folgers coffee containers)
Very long piece of string
Punch a small hole in the bottom of each cup and thread one end of the string through hole and tie knot. Attaching a cup to each end of the string.
One person takes each cup and play telephone. Works best when your sitting around the corner from one another or run the string under a closed door so you can't see one another.
Kids think its funny.
Ill be doing this tomorrow with my daughter.