Sean Maher is an American actor, probably still best known for his ensemble role on the all-too-brief Firefly as Dr. Simon Tan. He apparently shot down numerous takes by calling Summer Glau by her real name, instead of the character's, River. He has become a high profile gay activist, and he and his partner adopted a girl and boy. After his daughter's birth he was a stay-at-home dad for a couple of years. On HT, he played Aaron Cooper in "Embassy Row".