I found some Italian openings and couple of episodes of Three's Company. Over there, it is called Tre Cuori in Affito. For some weird reason in the third version, Lana and Terri both are credited in the same episode. Strange, because they weren't even on at the same time.
Version 1 (full episode):
http://www.youtube.com/watch?v=js7NaG9x4I4&feature=related
Version 2:
http://www.youtube.com/watch?v=mE3php_x0m0
Version 3:
http://www.youtube.com/watch?v=tu9eYp8yZEo