WWII

Me (after reviewing the causes of the Great Depression):  "So, does anyone know what led us out of the Great Depression for good?"
(no students answer)
Me:  "Like was there something that happened in the 1940s that put people back to work?"
(silence)
Student (semi-confidently):  "The twin towers falling?"
(silence)
(class stares at the student)
Me:  "Well...that happened in 2001.  So, ummm no."