The television is often called an idiot box.
idiot box definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
Slang television or a television set
idiot box definition by American Heritage Dictionary
noun SlangThe American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
idiot box - Phrases/Idioms
A television set, as in There they sit in front of the idiot box, hour after hour. This slangy and pejorative expression dates from about 1960.