I am looking for the name of a science fiction TV show from the late 70ies or early 80ies.
In the show small aliens used a fist-sized rock as their ship to explore their environment here on earth. A detail that I remember was that the rock had something like a periscope to observe the outside world. The key plot element of using the stone was to be very stealthy but unfortunately I can't remember more specific details.
While watching Portlandia (Season 2, Episode 8) I think the 'alien fruit' might be a reference to that TV show but I am not absolutely certain and googling did not provide any further hints.