Actors always associated with two separate roles

Aahnold as Conan and The Terminator.

Boris Karloff as Frankenstein’s monster and The Mummy.
Mel Gibson in Road Warrior and in Lethal Weapon.
David B. in Buffy/Angel and in Bones.
Christopher Heyerdhal (probably misspelled) as multiple characters (especially John) on Sanctuary and as the demon Alistair on Supernatural.
whatsisname, the guy who was on Quantum Leap and then Stargate.

Cock Knocker

Literary types remember Neal Cassidy as the protagonist in Jack Kerouac’s classic “On The Road” (under the name of Dean Moriarty), and the bus driver for Ken Kesey’s band of Merry Pranksters in Tom Wolfe’s classic “The Electric Kool-Aid Acid Test.”

Harry Morgan: Bill Gannon and Sherman Potter

and Pete Porter

William Conrad as Cannon and Jake and the Fatman (both sucked). He maybe had more acting roles on radio than tv. He did tons of voice over work/naration for tv and radio, his voice is way better known than his face.

Shatner is a far better comedic lawyer than dramatic cop or Starfleet captain. Though i think Star Trek was a comedy, the little bit i watched i was always laughing which didn’t go well with others.

Bogart as Rick Blaine and Sam Spade

Perhaps most memorable to me was his Matt Dillon on radio’s Gunsmoke!

Orson Welles: Charles Foster Kane and Harry Lime.

Alec Baldwin: Jack Donaghy and Blake (from Glengarry Glen Ross).

I think the two things he’s most often remembered for are Citizen Kane and his War of the Worlds radio broadcast.

Gordon Jump: Arthur Carlson and the chld molester on Different Strokes.

Jesus on Star Trek! Nobody has mentioned Jeffrey Hunter yet?

Dare I mention Carroll Spinney? He played a rather large bird and a trash-talking grouch.

Agnes Moorehead did decades of radio, was Margo Lane (one of them) on the Shadow. She was also Endora on tv Bewitched, which she didn’t think serious, didn’t think would succeed and didn’t want to be remembered as because she liked drama.

Orson Welles was one of the actors doing the Shadow on radio. He did lots as producer and directing in radio. He also was Harry Lime on radio as well as film.

Eddie Albert as Oliver Douglas and Warden Hazen

Alan Rickman: the Sheriff (of Nottingham) and Severus Snape. And Hans in Die Hard. And the Colonel in Sense & Sensibility.

i’ll always think of him as Marvin

in my foraging for a bit of other trivia

Parley Baer who did a lot of radio work, periodic reoccurring roles, maybe best known as Chester on Gunsmoke.

He was in lots of singular roles on tv and periodic reoccurring roles like Dr. “Doc” Appleby in the The Dukes of Hazzard; Miles Dugan in The Young and the Restless.

Similar thread here.

I think no one in this thread has mentioned Julie Andrews; who, to the not-really-into-musicals-crowd, is vastly better known for The Sound of Music and Marry Poppins than anything else.

Mr. T: B.A. Baracus and Clubber Lang

George Peppard: Hannibal Smith and Lt. Bruno Stachel (The Blue Max).

Yeah the last one’s a huge stretch, but I wanted my all A Team post.

Personally, I don’t associate Orson Welles with roles at all, but rather, with his directing.