As someone who watched and actually enjoyed the short-lived Ferris Bueller TV show, Jennifer Aniston will always be Jeannie Bueller to me. Normal people associate her with Friends but, to me, that was just Jeannie Bueller’s new show. Jeannie Bueller was really good in Horrible Bosses.
I was amazed to realize that after watching it for the n[sup]th[/sup] time she was also Miles Dyson’s wife in Terminator 2 !
Yeeeeah, it’s Gary Cole as Bill Lumbergh in that one, that would be greeeat…
Oh yes, me too! No matter what he was in, I couldn’t shake the creepy vibe. He was riveting in an awful way on GL.
We’ve had similar threads before:
Kyle Maclachlan is Dale Cooper.
David Duchovny is Fox Mulder.
Christopher Lloyd is a tossup between Jim Ignatowski and Doc Brown.
Danny DeVito is Louie De Palma.
Judd Hirsch is Alex Rieger.
Marilu Henner is Elaine Nardo.
Tony Danza is Tony Banta.
Michael Richards is Cosmo Cramer.
Jason Alexander is George Costanza.
Julia Louis-Dreyfus is Elaine Benes.
Of course Jerry Seinfeld is Jerry Seinfeld. I can’t even imagine him playing some fictional character.
Ted Danson is Sam Malone.
Shelley Long is Diane Chambers.
Rhea Perlman is Carla Tortelli.
Michael J. Fox is Marty McFly (although I do like his lawyer character).
I could probably list hundreds but I guess I should stop.
Sean Penn will always be Spicoli, dude.
Billy Crystal will always be Jody.
It actually took me several episodes of Nashville to notice that Deacon Claybourne was Chip Esten from Whose Line, but once I did I couldn’t un-notice it.
If I ever met Wayne, I’d want to ask if anyone from LMaD ever tickled his fig old futt.
Judith Light was on One Life to Live, and was on the witness stand, where she sobbed through her testimony. Now, whenever we see her on TV, my husband or I will say “Oh, Karen the crier is on this.”
He will always be Phoebe’s brother Frank on Friends to me.
She’s Angela Bower.
No, Cesar Romero is and always will be! 
John Larroquette will always be Dan Fielding. I always though Boston Legal missed an opportunity by not doing some sort of reference to Night Court.
I caught the last half of Con Air as I was channel hopping earlier for the first time since it was released. I was surprised to see Lost’s “Other” Mr. Friendly (M.C. Gainey) piloting the plane.
No matter how many serious cops or sitcom dads he plays, Jeremy Sisto will always be the guy who sliced off his own tramp stamp.
You both need to see Amazon’s “Transparent”, it might cure you.
Alan Dale will always be Jim Robinson from Neighbours.
Hmmm. I disagree with most of these, in the sense that I don’t see most of those actors restricted to those roles. (Marlon Brando IS Don Corleone? Seriously? There’s a (fading) generation to whom he IS Stanley Kowalski) About the only one I agree with is Paul Scofield being Sir Thomas More. When I see him in The Train or Quiz Show, it looks like the Chancellor of England has stepped in a time machine.
My picks:
Howard da Silva is Benjamin Franklin. I’ve seen him in other things, but he’s definitely Ben Franklin from 1776
Ben Kingsley is Mohandas K. Gandhi. Even when he’s in cheesy SF movies, I have to ask what the Mahatma is doing slumming there.
Kevin McCarthy is Miles Bennell – who? – That Guy From Invasion of the Body Snatchers ("You’re Next! You’re Next!!!). Even when he’s in Mirage or playing a Bad Guy in a 1980s or 1990s movie, he’s that Guy From IotBS.
Ray Liotta will always be Another World’s Joey Perrine for me.
Frank Gorshin is The Riddler. Even when he was Commissioner Beale on Star Trek, he was The Riddler.
BEALE [Jumps out of turbolift in pink tights and turtleneck]: Riddle me this, Captain Kirk…!