Jason “Rael” Evers and Jay “Petri” Robinson in the Hawaii Five-O episode “Cloth of Gold.”
Lee Meriweather, a regular on “The Time Tunnel” as Losira in the TOS episode, “That Which Survives”.
A time tunnel journey into the future has hallways that resemble the interior of a Romulan ship in “The Enterprise Incident”. Both series were filming at the same time; I wonder if they shared stages and props.
It’s possible, I suppose. IIRC, TT was filmed at 20th Century Fox, but there weren’t that many stories set in the future. Desilu/Paramount, on the other hand, did a lot of renting out to different production companies, so TT might have used one of their ST sets for that particular episode.
Just saw the great 1993 Harrison Ford/Tommy Lee Jones chase thriller The Fugitive, and spotted several ST alums in it.
That is the only episode I’ve seen from the future. I don’t recall how often I watched it as a child.
Thanks, terentii.
Just saw Brian George–Babu Bhatt on Seinfeld–playing Julian Bashir’s father on DS9.
Michael “Kang” Ansara without his toupee as “Mob Boss Piro Manoa” in the Hawaii Five-O episode “Death Is a Company Policy,” the first of the fifth season and without Zulu as “Kono.”
Anthony Caruso, Bella Oxmyx in “A Piece of the Action” in Peter Gunn, “The Coffin” as "the scar-faced Ramon DeCara " a Mexican bad guy.
I am being redundant, as though Anthony Caruso would play a character who was not a bad guy.
Ricardo “Khan” Montalban and Diana “Dr Pulaski” Muldaur as race car enthusiast “Alex Pareno” and his fiancee “Angela” in the Hawaii Five-O episode “Death Wish on Tantalus Mountain.”
This has to be the worst episode ever of a series that had plenty of stinkers. 
Captain Kirk himself, bare-chested and sporting a '70s toupee and Texas accent, in the Hawaii Five-O episode “You Don’t Have to Kill to Get Rich … But It Helps.” He’s a PI from the mainland who tries to blackmail blackmailers. This one takes the cake!
That’s pretty good. terenti, but I’ll bet that .38 in the last bit was on “stun”.
“Ah … ooooown … yew!” 
Just finished a rewatch on the old SF series “Time Trax”. The premise was that a number of fugitives escaped justice by retreating 200 years into the past, to our present, with the help of an evil scientist. Among those were Jerry Hardin, Edward Albert, Eric Pierpoint, John DeLancie, Cliff DeYoung, and John Schuck. Other Trek actors appearing in the series were Henry Darrow, Ronnie Cox, Bernie Casey, Jeri Ryan, and Kerrie Keane. (Keane and Pierpoint alson headlined the “Mr. and Mrs Fugitive” series “Hot Pursuit”.) The lead character was tasked with tracking down those fugitives and returning them to the future.
As an aside it occurred to me that an episode of that series could have had a contemporary FBI agent, say, connect the disappearances of these people from the present to the activities of the protagonist.
That first scene was like the setup for Hawaii Porn-O.
“That’s sooooo helpful!” 
I believe the proper Kirkian accent is, “I…ownyou!”
Kevin Lynch, the head miner in “Devil in the Dark”, as Marshall Guy Lamport in the Have Gun Will Travel episode, “The Marshall’s Boy”.
I believe he was in every western TV series ever made.
I was a little surprised to see Teri Garr as Gene Hackman’s girlfriend in The Conversation, a few years after her ST:TOS appearance and a few years before CE3K. I’d forgotten she was in that.
The 1991 film “The Rocketeer” features 4 TNG alumni. Billy Campbell (Okana) as the star, Paul Sorvino (Worf’s human brother), Ed Lauter (Commander Albert) and Lost’s Terry O’Quinn (Admiral Pressman) as, get this, Howard Hughes.