<Ul> <Li> John Lithgow as Dick Solomon : Though the High Commander and head of the expedition to Earth , he is often the most childlike member of the group , being , ironically , the youngest of the crew , despite being the oldest family member ( at least appears to be the oldest due to his body ) . Much of the behavioral or societal - based troubles faced by the crew in their mission while on Earth frequently arise from some juvenile act perpetrated by Dick , troubles which in turn are forced to be overcome by the entire troupe with a great deal of reluctance . </Li> <Li> Kristen Johnston as Sally Solomon : With a rank of lieutenant , she is the security officer and second - in - command . She has been called Dick 's sister , but was sometimes introduced as Tommy 's sister earlier in the series , and , on one occasion , claimed to be his mother , although never Dick 's daughter and certainly not his spouse ; failure to clarify the exact relationship between Tommy , Harry , and Sally led to humorous confusion whenever either Harry or Sally attempted to act as Tommy 's guardian . Sally was chosen to be the woman because she apparently lost some sort of contest and was not too thrilled about it ; while the alien species is described as asexual , Sally seems to have a harder time trying to figure out womanhood than the others do manhood . She files a request to be made male early in the mission , though later decides she liked being a woman . A later episode had Dick and her switching bodies on orders from the Big Giant Head , which caused much confusion both on their parts , as they had gotten used to their respective genders while on Earth , and the other characters , as they could not get used to Sally acting like Dick and vice versa . </Li> <Li> French Stewart as Harry Solomon : Originally , he was not part of the mission , but just happened to go for the ride because an extra seat was available . Later , it becomes known that a chip is in his head , and he becomes the Communicator or Transmitter . Occasionally , he gets a message from the Solomons ' leader , the Big Giant Head , and shakes violently in the middle of a sentence and squats down , with his arms at 90 ° angles , declaring `` Incoming message from the Big Giant Head ! '' , before going through the motions of delivering the message , which always ends with a violent sneeze . He poses as Dick and Sally 's brother , and Tommy 's uncle . Harry is often known to be the simplest family member , is occasionally impulsive and misunderstands people . He is also prone to misfortune . Though he seems to fit in on Earth with the earthlings better than anyone else , this is implied because he is seen as dimwitted . Whether he is really dimwitted or just more sensitive to his surroundings is unclear , however . </Li> <Li> Joseph Gordon - Levitt as Tommy Solomon : Information officer and third - in - command behind Sally , Tommy plays the role of Dick 's adolescent son , yet he is the oldest and smartest of all the aliens . Throughout the series , Tommy continually reminds the others of his superior intelligence and greater age . Gordon - Levitt left the series ( after the fifth season concluded ) as a primary character , only appearing as a recurring character in just over half the episodes of season six . In the show , this is explained by Tommy 's graduating from high school and moving out to college . </Li> <Li> Jane Curtin as Dr. Mary Albright : Dick 's colleague and on - and - off girlfriend , Mary is aware that Dick is an insensitive idiot , but appreciates his joie de vivre and quirkiness . Reference is often made to the insecurity caused by her bad parenting , and the fact that before Dick arrived , she was known for sleeping around , and had even been nicknamed `` Dr. Slutbunny '' . </Li> <Li> Simbi Khali as Nina Campbell ( seasons 3 - 6 , recurring previously ) : Dick 's and Mary 's administrative assistant , she finds Dick beyond the pale . </Li> <Li> Elmarie Wendel as Mrs. Mamie Dubcek ( seasons 3 - 6 , recurring previously ) : Mrs. Dubcek is a `` blast from the past '' , namely the '
<Ul> <Li> John Lithgow as Dick Solomon : Though the High Commander and head of the expedition to Earth , he is often the most childlike member of the group , being , ironically , the youngest of the crew , despite being the oldest family member ( at least appears to be the oldest due to his body ) . Much of the behavioral or societal - based troubles faced by the crew in their mission while on Earth frequently arise from some juvenile act perpetrated by Dick , troubles which in turn are forced to be overcome by the entire troupe with a great deal of reluctance . </Li> <Li> Kristen Johnston as Sally Solomon : With a rank of lieutenant , she is the security officer and second - in - command . She has been called Dick 's sister , but was sometimes introduced as Tommy 's sister earlier in the series , and , on one occasion , claimed to be his mother , although never Dick 's daughter and certainly not his spouse ; failure to clarify the exact relationship between Tommy , Harry , and Sally led to humorous confusion whenever either Harry or Sally attempted to act as Tommy 's guardian . Sally was chosen to be the woman because she apparently lost some sort of contest and was not too thrilled about it ; while the alien species is described as asexual , Sally seems to have a harder time trying to figure out womanhood than the others do manhood . She files a request to be made male early in the mission , though later decides she liked being a woman . A later episode had Dick and her switching bodies on orders from the Big Giant Head , which caused much confusion both on their parts , as they had gotten used to their respective genders while on Earth , and the other characters , as they could not get used to Sally acting like Dick and vice versa . </Li> <Li> French Stewart as Harry Solomon : Originally , he was not part of the mission , but just happened to go for the ride because an extra seat was available . Later , it becomes known that a chip is in his head , and he becomes the Communicator or Transmitter . Occasionally , he gets a message from the Solomons ' leader , the Big Giant Head , and shakes violently in the middle of a sentence and squats down , with his arms at 90 ° angles , declaring `` Incoming message from the Big Giant Head ! '' , before going through the motions of delivering the message , which always ends with a violent sneeze . He poses as Dick and Sally 's brother , and Tommy 's uncle . Harry is often known to be the simplest family member , is occasionally impulsive and misunderstands people . He is also prone to misfortune . Though he seems to fit in on Earth with the earthlings better than anyone else , this is implied because he is seen as dimwitted . Whether he is really dimwitted or just more sensitive to his surroundings is unclear , however . </Li> <Li> Joseph Gordon - Levitt as Tommy Solomon : Information officer and third - in - command behind Sally , Tommy plays the role of Dick 's adolescent son , yet he is the oldest and smartest of all the aliens . Throughout the series , Tommy continually reminds the others of his superior intelligence and greater age . Gordon - Levitt left the series ( after the fifth season concluded ) as a primary character , only appearing as a recurring character in just over half the episodes of season six . In the show , this is explained by Tommy 's graduating from high school and moving out to college . </Li> <Li> Jane Curtin as Dr. Mary Albright : Dick 's colleague and on - and - off girlfriend , Mary is aware that Dick is an insensitive idiot , but appreciates his joie de vivre and quirkiness . Reference is often made to the insecurity caused by her bad parenting , and the fact that before Dick arrived , she was known for sleeping around , and had even been nicknamed `` Dr. Slutbunny '' . </Li> <Li> Simbi Khali as Nina Campbell ( seasons 3 - 6 , recurring previously ) : Dick 's and Mary 's administrative assistant , she finds Dick beyond the pale . </Li> <Li> Elmarie Wendel as Mrs. Mamie Dubcek ( seasons 3 - 6 , recurring previously ) : Mrs. Dubcek is a `` blast from the past '' , namely the '
who starred in 3rd rock from the sun
who starred in 3rd rock from the sun
John Lithgow Kristen Johnston French Stewart Joseph Gordon - Levitt Jane Curtin Simbi Khali Elmarie Wendel
John Lithgow Kristen Johnston French Stewart Joseph Gordon - Levitt Jane Curtin Simbi Khali Elmarie Wendel Wayne Knight