Star Trek: 10 Things You Didn't Know About Tasha Yar
2. What She Did In The Shadows
If you're going to have a tragic backstory, you might as well have two, or technically even three. There is little worse than the childhood Tasha Yar had to suffer through, and we'd assume that at least the first seven years of her alternate's life were identical. What's most tragic about the Yar that went back on the Enterprise-C, however, is that she was executed for trying to escape the clutches of her Romulan captors, and it was her own flesh and blood who essentially ratted her out.
The vampiric Sela — alternate Yar's treacherous (if young at the time) daughter — first appeared in the shadows in The Mind's Eye, only to emerge at Redemption's end to really stir the galactic pot of viinerine (and/or blood pie in this case). Sela returned later, of course, to throw a coil spanner in the works of Spock's attempts at reunification by trying to invade Vulcan.
In point of fact, that Yar had survived the trip back to the past, been captured by the Romulans, and had a daughter (although apparently at first with Lt. Castillo) was Denise Crosby's idea. As Crosby described it in a 1991 interview included on the TNG season four DVD extra Chronicles From the Final Frontier, the whole concept for Sela came about in one afternoon when she was thinking back to the fun she'd had filming Yesterday's Enterprise. Crosby made sure the idea "was pretty tight" and then pitched it to producers.
They seemed convinced, but Redemption writer Ronald D. Moore was dubious at first. Moore gave his initial reaction to the Sela proposal in Chronicles From the Final Frontier, saying "Well, she's dead twice now. What do you mean she wants to come back?" "That's insane!" Eventually, the idea grew on him to the point of obsession, and he made Sela the cliffhanger!