KNOCK-KNOCK JOKE

FIRST PERSON: I HAVE A NEW KNOCK-KNOCK JOKE, DO YOU WANT TO HEAR IT?
SECOND PERSON: YES.
FIRST PERSON: YOU START.
THE SECOND PERSON WILL ALMOST ALWAYS START AND WHEN YOU SAY WHO'S
THERE THEY WILL BECOME CONFUSED AND THEN REALIZE WHAT YOU HAVE DONE.

Where learned: PENNSYLVANIA ; SAINT CLAIR

James Callow Keyword(s): CATCH

Date learned: 00-00-1969