I was going to suggest Anne Francis. I just started Netflixing The Man from U.N.C.L.E.
, and she's in the third episode -- and makes a stunning brunette.
And it's surprising and disappointing that Roddy McDowall never did a Trek episode. He would've made an awesome Trelane.
Oh, and Greg, Joan Collins also did both ST and Batman
, appearing as the Siren in the third season of the latter. Other actors who did both include Roger C. Carmel, Stanley Adams, Malachi Throne, Grace Lee Whitney, John Crawford, Leslie Parrish, Nancy Kovack, and more.