Play on Words:  Simple Truths.  By taking the literal meaning of a key word, we surprise the audience, who's automatically interpreted the expression with its traditional reference....the first part is a cliche or first sentence is a cliche.  The 2nd part (punch line) is an unexpected interpretation that's realistically literal. Example:  My wife went shopping yesterday, and came home with 7 windows.

Helitzer, Comedy Writing Secrets