What, a peck on the cheek so quick that it could only be measured by sports finish-line equipment?
I didn’t see this mentioned:
Katie Aselton and Mark Duplass are married in real life, but on “The League” she is married to Stephen Rannazzisi.
Ken Olin and Patricia Wettig are married in real life, but were married to different people on “Thirtysomething”
John Astin & Patty Duke and James Taylor & Carly Simon were all guests on the first episode of the 45 minute The Music Scene. The first two and the second two couples married and subsequently divorced.
Lee Majors and Farrah Fawcett appeared together on The Six Million Dollar Man in 4 episodes (maybe some other shows).
Farrah Fawcett also was in a TV Movie with Ryan O’Neal in 1989
She chatted with him in the first episode of The Fall Guy, to show there were no hard feelings. (With, y’know, bonus points for making it into the theme song.)
Griffith and Johnson were also in a 1985 episode of Miami Vice together. This was in between their two marriages to each other.
Shirley Temple and her first husband John Agar made two movies together: “Fort Apache” (first of John Ford’s acclaimed “cavalry trilogy”) and the less successful “Adventure in Baltimore”.
Also were Tom Cruise and Penelope Cruz a couple in Vanilla Sky?
Kristen Bell and Dax Shepard have appeared together as a married couple in several Target commercials – does that count? 
Playing fictionalized characters of themselves… I’ll allow it. 
I remember seeing Bacon and Sedgwick together in a little early 90s film called (I think) Singles. Shortly thereafter they were married, as I recall.
I think Johnny Galecki got tagged with the “maybe he’s gay” when he had a couple of gay film roles prior to Big Bang Theory - Bounce is the one that comes to mind, but I think there was a couple more.
Much like the guy who played Lex Luthor on Smallville - he played a cross-dresser in a number of films prior to that and of course the whispers started.
FX’s - The Americans - Keri Russell and Matthew Rhys
Married on-screen
Dating off-screen (she actually left her real husband, for him)
In the animated classic “Cars” the voices of Strip “The King” Weathers and his wife Lynda “Mrs The King” Weathers are done by Richard and Lynda Petty.
Mac and Dee are married (or were) in real life I believe.
Real names, Rob McElhenny and Kaitlen Olsen.
Malcolm McDowell and Mary Steenburgen made Time After Time (playing H.G. Wells and his love interest) and were subsequently married for several years.
Steenburgen and her current husband Ted Danson met on the set of Pontiac Moon in 1994, got married a year later, and co-starred in the short-lived series Ink in 1996.
Bollywood actors have a very high incidence of RL married couples playing onscreen married couples. I’ll just mention a few of the real famous ones:
Amitabh and Jaya Bachchan
Saif Ali Khan and Kareena Kapoor Khan
Abhishek and Aishwarya Rai Bachchan
Ajay Devgn and Kajol
Hema Malini and Dharmendra
On the lips.
Yes. The plot revolves around that relationship.
They were a couple on Brothers & Sisters. Speaking of which…
I thought he was gay, and not just because of his character on B&S, I swear I read an article while the show was on about him and his character both being gay.
And can I just give a hearty BOO to anyone mentioned in this thread as dumping their spouses for costars? Fuckin hollywood…