Rosalind Chao brought Keiko O’Brien to life on Star Trek: The Next Generation, but she was originally a favorite to play security chief Tasha Yar. Keiko played a supporting but integral role in the dynamics of The Next Generation’s crew, showing the civilian and domestic sides of life in Starfleet, and she continued her part on Deep Space Nine. She and Miles O’Brien were one of the few successful relationships in Star Trek’s long history of failed romances, showing that not every partnership was doomed to tragedy. However, Keiko didn’t appear until season four, and Chao could have had a large role in the show from the beginning if the original casting had not changed.
While the revival of the Star Trek franchise was still in development, castings were in flux, with the favored actors for different roles changing over time. Five actresses were in consideration for the role of Tasha Yar, with Rosalind Chao in the lead. However, the list of candidates for Tasha Yar at that time did not even include Denise Crosby, who eventually won the role.
Denise Crosby was instead the only candidate to play Deanna Troi, the part she had initially auditioned for, but like most of the castings, this was still up in the air. Even Captain Picard was a tight contest among several actors, so the rest of the bridge crew was far from certain. Crosby’s casting changed when Gene Roddenberry took a liking to Marina Sirtis, who had also auditioned for Tasha Yar. The showrunners preferred Sirtis for the role of Troi because she seemed more exotic, so the parts were switched, and Crosby ended up with Yar. Unfortunately, this also left Rosalind Chao without a part in the early seasons.
If Chao had been cast as Tasha Yar, it would have changed the trajectory of the character and the dynamics of the crew for the rest of the series. After only one season, Tasha Yar was killed off when Denise Crosby requested to leave the show. Given that Chao remained on two different series as Keiko, she might have decided to stick with Tasha Yar for longer. Yar could have been further developed over several seasons, though the show may have missed out on the unique opportunity to feature a version of Tasha Yar from an alternate timeline and her half-Romulan child. Those interesting twists were brought about by Crosby’s amicable departure and return, though Chao’s Yar could have had multiple plotlines revolving around the character in the later season.
Star Trek may have played out in a vastly different way with Rosalind Chao in the role of Yar. She would have been the only Asian-American member of the main cast, adding more diversity to the bridge crew, and she likely would have played Yar in a different manner than Crosby did. Tasha Yar’s continued involvement in the show could also have greatly expanded the character’s story, especially since Star Trek: TNG did not hit its stride until season 3, so the original Yar didn’t have a chance to benefit from the peak of its writing quality. While Denise Crosby was excellent as Tasha Yar and her returning counterparts, the possibility of Rosalind Chao’s Yar is a glimpse at a version of Star Trek: The Next Generation that might have been.