I always thought the play's name was "Our American Cousin".
The play Tad was attending that evening:http://deadconfederates.files.wordpress.com/2010/08/aladdin.jpgFrom here.Also, next left column, lower down, announces that General Grant would be attending Ford's Theater that night with the Lincolns -- which of course changed to Clara Harris and her fiance, Major Rathbone, at the last minute.
Thanks for that Andy. And Pat - yes, you're correct...it is Our American Cousin. I guessed the ad guy missed the mark on this one.