Also Robert Duvall.
Pointless WoO trivia: They had already recorded all the songs, and the film was waaaay over budget, so when Buddy Ebsen dropped out due to the make-up allergy, they didn’t bother to re-record the songs. If you listen carefully, you can hear his distinctive voice singing, “We’re off to see the Wizard…”
Melvyn Douglas underwent an amazing transformation as he aged. As a young actor he was noted for light comedies,and had matinee idol good looks. Segue through the 40’s and 50’s, his share of dramatic roles increased as his face became more craggy. In his later years he was almost unrecognizable from his much younger days in films, such as, “Being There”, “Hud”, and many more.
He didn’t age. He evolved. Or devolved…
Young Bill Shatner was dubbed the Male Fay Wray for his screaming ability.
A young, but still uniquely odd looking Leonard Nimoy was cast in various other worldly roles and as bad guys.
The young John Wayne was rather thin, and I can’t can’t find a good pic!
Sam Beckett’s cigar chomping holographic pal Al is unregognisable as The boy With Green Hair
There may be some stray Ebson in a chorus or two, but it’s definitely Haley’s voice on “If I Only Had a Heart.” For that matter, Haley’s voice is also in the recorded and filmed, but unused, number, “The Jitterbug.” Ebson’s performance of “IIOHAH” with stills of his costume and make-up tests, and Haley and cast’s recording of “The Jitterbug” along with home movie footage of dance rehearsal are included in a number of WoO DVD releases.
I just saw him in a 1968 movie yesterday! Five Card Stud. He was young alright.
He was also one of the criminals in 1968’s The Thomas Crown Affair.
Another early *Bonanza * (“Gift of Water”–11 Feb. 1962) features James Doohan *and *Majel Barrett.
You must have misread the credits. Irene Ryan and Cary Grant never made a movie together. Nor was Ryan a cute, young babe in the 1930s. She was a plain-looking, skinny-necked comic character actress.
Maybe you’re thinking of Irene Dunne with Cary Grant in The Awful Truth and Penny Serenade.
She didn’t make any movies in the 1930s. First movie role in 1943.
I have just the opposite experience, usually, but it’s just as jarring.
I watch a lot of silents and pre-codes, and when I finally started watching newer movies ('40s, '50s) I would see people that I had only ever seen young before. That was weird. It was, to me, as though they had aged overnight. Watching The Bachelor and the Bobby-Soxer was weirder more for the older (but still gorgeous) Myrna Loy than it was for seeing a grown-up Shirley Temple.
Alec Ginness was Yevgraf Zhivago prior to Obi-Wan.
You took the words right out of my mouth. 
Spock on Bonanza. Seems Star Trek really was a Wagon Train to the stars. 
Lots of Star Trek folk were in previous TV series (Shatner and Nimoy both appeared in the same episode of The Man from U.N.C.L.E. pre-Star Trek), so that’s not a surprise.
What isd a surprise is Nimoy as an extraterrestrial in Zombies of the Stratosphere.
Regarding Bernard Lee, I’ve always been srprised at how young he looks in ** The Third Man**. The James Bond films started not all that much later, but even in Dr. No Lee looks like an aged curmudgeon.
One of the more interesting deliberate examples of juxtaposed old and new was an episode of , I think, Murder, She Wrote where they took scenes out of some old movie to use for flashbacks, then got the same now-aged actors to portray their older selves. You really can see how they aged. IIRC, Henry Morgan was one of the actors, so you get to see his old and new self side by side. (Morgan was in a lot of TV series since the 1950s, always with white/grey hair. I suspect he looked old before his time, which is why he seemed to be the same age for so long. Not opnly Dragnet, but also Kentucky Jones and December Bride. It’s kind of shocking to see him with dark hair.)
I had a similar experience with him in The Ladykillers (1955)