As time passed from Skin of Evil, Denise Crosby changed her mind, and she comes back later as a guest star for a single episode. She doesn't play Tasha Yar. She plays a new character
After that, Denise Crosby made a documentary film named Trekkies, in which she says that maybe it wasn't such a good idea to leave the show so early as Skin of Evil
***WARNING MASSIVE SPOILER ALERT TC DO NOT READ***
Denise Crosby came back THREE TIMES in Star Trek. She played Tasha Yar in the brilliant Yesterday's Enterprise, then played The Half Romulan Sela in Redemption and then played Yar again in the series finale All Good Things.
I suggest you do some research before posting.
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All your base are belong to us. Been gaming since 1979. Xbox Live Account Sophitia99