Sorry Mrrzy ol bud..
--Ok, Dianna Muldaur played the blind embassador (help can't remember the episode!) and a doctor (shock horror) in "Is There No Truth In Beauty?"
--William O. Campbell played Trelaine in "The Squire of Gothos" and Koloth in "The Trouble With Tribbles." He also played Koloth in Deep Space Nine--can't remember the name! Dang it, when is Larry Nemechek gonna come out with the DS9 Companion so I can memorize all those episodes too!
Actually, the actor who played Sarek (darn can't remember his name!) first appeared as the Romulan Warbird commander in "The Balance of Terror" which is the first appearance of Romulans ever ("They killed the Centurion!") and one of my fav TOS episodes. "The Enterprise Incident" was the one with the female Romulan commander who "captured" Spock & Kirk.
As for multiple series players, well! That's a lot of fun...unfortunetly I'm at school right now and this tiny iMac keyboards are hard to type a lot on, especially with classical guitar player fingernails! I actually could name so many multiple players it would take forever to list them all! My sister and I have this "thing" with finding all the multiple series players...long list!

Dang you're a lotta fun to have here, Mrrzy! For fun, try looking up "Star Trek parody of "Master of The House" thread in the archive--tell me what you think!

--Mbo