Chinese whispers

noun (functioning as singular)

a game in which a message is passed on, in a whisper, by each of a number of people, so that the final version of the message is often radically changed from the original
any situation where information is passed on in turn by a number of people, often becoming distorted in the process

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012