What were the main family in the American television sitcom "3rd Rock From The Sun"?

"3rd Rock from the Sun" is an American television sitcom created by Bonnie and Terry Turner, which originally aired from January 9, 1996, to May 22, 2001, on NBC. The show is about four extra-terrestrials who are on an expedition to Earth, the third planet from the Sun, which they consider to be a very insignificant planet. The extra-terrestrials pose as a human family to observe the behavior of human beings.

The show premiered three years after the film "Coneheads", which was also written by the couple and featured a similar premise of extra-terrestrials arriving on Earth and assimilating into American society.

The family often communicates through Harry with their off-world (and usually unseen) boss, the Big Giant Head, who when he finally visits Earth, is played by William Shatner. Harry unexpectedly (and often in inconvenient circumstances) stands up, his arms stiff (acting as the antenna), and proclaims: "Incoming message from the Big Giant Head!"