What is the word for a joke which is told as real thing?

Is there any single word for a joke which is initially told by somebody as a real thing, then when person is fooled, the person disclosing the information that it's just a joke? Like April Fools' joke.

Solution 1:

Such a joke is often told with deadpan

Deliberately impassive or expressionless

Oxford Dictionaries Online

Example: "His deadpan tone made it difficult to tell whether my dog had actually been crushed by a piano."

This is typically only done in situations where one would expect the speaker to sound serious.

Solution 2:

While not a noun for the joke itself, the term straight face is often used to describe the demeanor of the teller

A blank or serious facial expression, especially when trying not to laugh: my father kept a straight face when he joked

Oxford Dictionaries Online

Note that this expression is also used to describe someone who is deliberately lying.