Ted: You know who I always see her with? The perfect guy for Mary? Clark Kent. Rugged, square jawed. A little shy, a little mild mannered...
Murray: ...and when he takes his clothes off - Superman.
This episode was filmed on September 26, 1975.
Perhaps this was an inside joke? ...Mary's JOE is in construction, whereas Rhoda's JOE (making a quick appearance -with Rhoda - in this episode) is in demolition!