A couple more celebrity guides I've been compiling via newspapers.com. I used the Tucson Citizen as my base but occasionally had to fill in elsewhere when celebs weren't listed or panels for "Rhyme and Reason" were incomplete.

First, "The Magnificent Marble Machine."

July 7: Florence Henderson & Roddy McDowall [VTR 6-24]
July 14: Leslie Uggams & Jan Murray
July 21: Vicki Lawrence & Robert Reed
July 28: Adrienne Barbeau & Jimmie Walker
August 4: Joan Rivers & Robert Fuller
August 11: Leslie Uggams & David Brenner
August 18: Susan Clark & Frankie Avalon
August 25: Jo Anne Worley & Arte Johnson
September 1: Marcia Wallace & Sam Melville
September 8: Nanette Fabray & Gary Burghoff
September 15: Joan Rivers & Bill Daily
September 22: Peter Marshall & Alex Trebek
September 29: Lee Meriwether & Gary Burghoff
October 6: Karen Valentine & Marty Allen
October 13: Betty White & Earl Holliman
October 20: Jo Anne Worley & Tony Randall
October 27: Michele Lee & Larry Linville
November 3: Jim McKrell & Chuck Woolery
November 10: Barbara Feldon & Roddy McDowall
November 17: Leslie Uggams & Jamie Farr
November 24: Jo Anne Worley & Earl Holliman
December 1: Florence Henderson & David Brenner
December 8: Ruta Lee & Alex Trebek
December 15: [preempted this week for “Noonday”]
December 22: Adrienne Barbeau, Leslie Uggams, Arte Johnson, Anson Williams
December 29: Joan Rivers, Jo Anne Worley, Jamie Farr, Earl Holliman
[on hiatus from January 5-16, 1976]
January 19: Lee Meriwether, Karen Valentine, Gary Burghoff, Arte Johnson
January 26: Betty White, Jo Anne Worley, Earl Holliman, Alex Trebek
February 2: Carol Lawrence, Leslie Uggams, David Brenner, Pat Harrington
February 9: Della Reese, Karen Valentine, Jamie Farr, Robert Fuller,
February 16: Denise Alexander, Jo Anne Worley, Gary Burghoff, Anson Williams [VTR 2-11]
February 23: Shelley Fabares, Nanette Fabray, Pat Harrington, Roddy McDowall
March 1: Adrienne Barbeau, Leslie Uggams, Earl Holliman, Arte Johnson
March 8: Ruta Lee, Rose Marie, Peter Marshall, Alex Trebek
March 15: Carol Lawrence, Jo Anne Worley, Charlie Callas, Robert Fuller
March 22: Leslie Uggams, Karen Valentine, David Brenner, Bobby Van
March 29: Florence Henderson, Lee Meriwether, Pat Harrington, Anson Williams
April 5: Nanette Fabray, Jo Anne Worley, Jamie Farr, Earl Holliman

The last original week was almost certainly April 5-9. "The Fun Factory" was supposed to have replaced "Machine" on Monday, April 12, but a strike by NBC employees starting April 1 caused a delay, according to an article in the NY Daily News of April 3 (page 33). The network elected not to use substitute crews due to the new show's complex production techniques. Writeup also stated that MMM repeats would begin April 12. Not many celebrity listings are found for it past April 9, but circumstantial evidence suggests that NBC reran the January 19 through March 19 shows from April 12 through June 11. Celebrities in the Tucson Citizen for the weeks of April 26 and May 24 match those of February 2 and March 1, respectively.

On to "Rhyme and Reason" . . .

Winning Lines is often considered one of the worst formats with one of the best bonus rounds.

I will say it again and every time, Winning Lines was created as a vehicle for UK's lottery. Not our fault that we didn't add some meat on the bone.

If you're Frank Wayne producing The Nighttime Price Is Right, you're treating the Showcase that way. 

Not for nothing, MattO is correct, most game shows are paced so that the end game will have the biggest pop for good or bad. I think it was Steve G. who told me that at least for a long time, the Showcases would have the biggest prizes, but not necessarily that the showcase winner wound up as top winner overall.

Yeah, it would be nice if they had more valuable prizes in the boxes on offer to make it a little bit more strategic as to when to keep a prize and when to exchange it. But then again, the whole fun of the round was watching the husband run up and down the stairs for 90 seconds and marvel at the fact that nobody ever took a tumble carrying those boxes without holding a handrail.

I typically don't stick around for it when stopping on a YT video, but I look at it this way--winning a stunt round allows the team to choose what sort of prize they want, and the end game ramps that up. Want kitchenware? Something to hang on your wall? Electronics? You could have a little of everything and there is the fun of "here's the next thing that you won" and generally the prizes were opened by retail value, so it built to a crescendo.

Best guess: maybe YDS! was in contention to take the time slot that eventually went to The Neighbors. Which in retrospect would have been the better choice.

Now I really want to see Dusty Springfield as a celebrity guest —if only for a few minutes.

maybe just three questions per round, as the free spins on the board can make up for earning fewer spins to start.

Pretty sure the Banks version is already three questions per round, isn't it?

A vote for Stewart's Winning Streak. Lame front game, but the end game, with some similarities to Beat The Odds, was good. Blindly picking letters one at a time and being challenged to use every letter picked in a single word for double the money each time was quite the challenge.