Since there's a similar thread for Gunsmoke, I thought I'd start a similar
thread for my favorite TV western, Bonanza.

Season 1:
Yvonne DeCarlo (1st episode, "A Rose for Lotta")
Jack Carson ("Mr. Henry T.P. Comstock")
Whitney Blake ("Vendetta")
Everett Sloane ("Blood on the Land")

Season 2:
Ricardo Montalban ("Day of Reckoning")
Neville Brand ("The Last Viking")
Leonard Nimoy ("The Ape")
Julie Adams ("The Courtship")
John McIntire and Adam West ("The Bride")
Claude Akins and Edgar Buchanan ("Sam Hill")

Season 3:
DeForrest Kelley ("The Honor of Cochise")
Robert Culp and Dabbs Greer ("Broken Ballad")
Arnold Stang ("The Many Faces of Gideon Flinch")
Sue Randall ('The Horse Breaker")
Royal Dano, Majel Barrett and James Doohan ("Gift of Water")
Lee Marvin ("The Crucible")
Inga Swenson ("Inger, My Love")

Season 4:
Denver Pyle ("A Hot Day for a Hanging")
William Demarest ("The Hayburner")
Aneta Corsaut ("The Way of Aaron")
Carroll O'Connor and Denver Pyle ("The Boss")

Season 5:
Jonathan Harris ("A Passion for Justice")
Judy Carne ("A Question of Strength")
Stefanie Powers ("Calamity Over the Comstock")
Jay C. Flippen and Butch Patrick ("The Prime of Life")
Keenan Wynn and Dave Willock ("Alias Joe Cartwright")
John Dehner ("The Gentleman From New Orleans")
Peter Breck ("The Cheating Game")
Denver Pyle ("Bullet for a Bride")
Guy Williams ("Return to Honor" and "Triangle")
Jesse White and Jerome Cowan ("The Saga of Muley Jones")
Joan Blondell ("The Pressure Game")

Season 6:
Ed Wynn ("Ponderosa Birdman")
Michael Rennie ("Once a Doctor")
Mariette Hartley and Everett Sloane ("Right Is the Fourth R")

Season 8:
Royal Dano ("A Man Without Land")

Season 9:
Tina Louise ("Desperate Passage")
Richard Anderson, Karl Swenson and Kevin Hagen ("Showdown at Tahoe")
James Whitmore ("To Die in Darkness")

Season 10:
Ossie Davis ("The Wish")

Season 11:
Les Tremayne and David Cassidy ("The Law and Billy Burgess")

Season 12:
Gene Evans ("The Trouble with Trouble")

Season 8 should include Wayne Newton and Zsa Zsa Gabor (?)

Season 8 should include Wayne Newton and Zsa Zsa Gabor (?)

You are correct. (I haven't seen those episodes, that I recall.)

Season 5: Dennis Hopper

Season 10: Larry Linville and Wally Cox

Also, Tom Bosley appeared once each in seasons 10 (with Cox) and 11.

Season 5 : Marlo Thomas

Wow, four cast members from Star Trek made guest appearances on Bananza. Leonard Nimoy in season 2 and DeForrest Kelley, Majel Barrett, and James Doohan in season 3.

Taking a look at my favorite Season 5 episode that aired in Nov. 1963, "Calamity Over the Comstock," guest starring Stefanie Powers as Calamity Jane.

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When Jane shows her attraction to Little Joe, the facial expressions
are just priceless. Michael Landon's reactions are really something:

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Stefanie Powers looks so beautiful and I love her over-the-top
performance. The actor playing Doc Holliday is well-chosen.

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Joe is highly relieved to have survived a close call in the presence of Doc
Holliday. Look at the incredible, gravity-defying updo for Stefanie's hair:

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I realize not everyone is a fan of this episode, but I like it so much.