practical joke

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A mischievous trick played on a person, especially one that causes the victim to experience embarrassment, indignity, or discomfort.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Something done for amusement to the detriment of someone else.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a prank or trick played on a person (especially one intended to make the victim appear foolish)