A nurse is doing her rounds on the psychiatric ward one night. On her first
round she stops to check on Dave, who is sitting on the end of the bed
holding on to an imaginary steering wheel. The nurse says, "Dave, what are
you doing?" He replied, " I'm driving to Chicago!" The nurse smiles and
moves on.

Later in the evening, she rounds again to find Dave still sitting on the
edge of his bed, 'driving'; then abruptly makes a gear-shift move and stops.
The nurse asks, "Dave, what are you doing now?" Dave replies, "I'm in
Chicago!" The nurse smiles and continues her rounds.

Across the hall, the nurse walks in on Rob and is horrified to see him
sitting on the edge of his bed, masturbating. She exclaims, "Rob! What are
you doing?!" Rob grins and says "I heard Dave's out of town, so I'm fucking
his wife!"