Here’s a quiz in celebration of Marathon 39.
Answers refer to films shown at the Marathon.
Some answers are subjective, as are some questions.
Many require levels of memory or attendance far superior to my own.
Sorry about any mistakes or poor phrasing.
See what you can do before looking @ the list of films shown or googling.
Answers will be provided as seems appropriate.
Mostly, enjoy.

1.      Most shown?
2.      A British Acad. Award winning actor has appeared in a dozen+ SF or fantasy films. Name 2 of the 3 shown at the Marathon.
3.      Simon Pegg's colleague, Nick Frost, co-starred in Paul. Name his other Marathon appearance.
4.      Jeff Goldblum has been in 5 Thon films. Name 4.
5.      Name the most shown feature film.
6.      Another title has been shown the same number as (5). But actually it was two different films. The title was?
7.      Ahnald’s been in 3. Name them.
8.      NED RYERSON!! Was repeatedly in ___?
9.      A French film occasioned a second US film, both shown at the Marathon. They were?
10.      Who received a Best Actor Oscar for his performance in a Thon film?
11.      Film versions of Stephen King works are legion. Name the only one shown at the Marathon.
12.      Philip K. Dick movies are almost as legion as those of King. Name 3 of the 4 shown.
13.      Can you name the written work that any of (12) was made from?
14.      Speaking of Pegg. Name his 2 Marathon appearances.
15.      Name the remake of High Noon shown at the Marathon. The title is part of a previous answer.
16.      Lots of zombies in lots of films. Which had 4 footed zombies?
17.      Inspector Clouseau’s boss (the actor) was in a twice shown Thon film. It was?
18.      Which film had the largest wingspan?
19.      The prolific David Cronenberg has had 5 films here. Since 2 were pretty obscure, name 3.

A few subjective questions. 

20.      Name 3 genuinely funny films. “Genuinely” is defined as causing you or other watchers to laugh out loud at least 3 times.
21.      Which film did you find the most genuinely scary? In very few words, care to say why?
22.      Biggest waste of time? Please no Folklore – too easy.
23.      Iron Giant & Fantastic Planet are my two favorite animated Marathon films. Neither for the quality of the animation. Yours?
24.      Name 3 films where dogs play significant roles. And yes, John Carter counts.
25.      The first Thon film that I ever saw in a theater was The Mysterians. Yours?
26.      Name a film that is the sole representative of a given country. There’s an easy answer, but can you think of anything more obscure?
27.      Upside down and backwards brings what to mind?
28.      Eating crow is a catchphrase. Who actually does it? (Well a black bird at least.)
29.      With the exceptions of Fonda & Weaver, few women act the lead in Thon movies. Name one.
30.      Mimsy Were the Borogroves,  by classic SF authors Henry Kuttner & C.L. Moore,  was the basis of what Marathon film?
31.      Other classic SF stories form the basis of many movies. Name at least 4 written titles which were changed for the movie version.
32.      Bela Lugosi starred in Dracula (never shown.) He was in at least 3 Thon films. Name 2.
33.      H. G. Welles films. Name 3. (There were 5.)
34.      Can you name a film that ends with a total non-sequitur? Hint. One of my favorite films ends with the lead staring at a large ringed planet. Other?
35.      Recently saw Killer Klowns From Outer Space. It contained what I thought was the worst acting ever shown on a movie screen. Not one performance. Every performance. Your nomination for the worst acted Thon film?
36.      Lots of bug movies: at least 6. Name 4.
37.      One critic said that Plan 9 From Outer Space was the worst film ever made. Name three actors therein.
38.      Movies have been substituted, both deliberately and due to supplier error. Name a movie that was substituted for a title of the same name. Hint. A star in the movie was highly regarded as a juvenile performer.
39.      Steve McQueen and Michael Landon each had their second movie shown at the Marathon. Name both.

Bonus.
Wheat Chex or Rice Chex.? Can you state briefly the origin of Chex?

Thank you for any time you expend.

Well, so far Frank (WOOHOO!) has gotten all but two of the first 19.  Christopher Plummer (Q2) meets most , but not all of the criteria. Not enough SR/Fantasy. And he's Canadian.   18 doesn't seem THAT obscure.
Carry on.

Well, 2, 18 & 28 remain, plus the subjective questions. Lots more answers to 31. I was thinking of Einstein from Back to the Future as part of the answer to 24, but Invasion ---is better. Thinking of a different lady for 29. For (26) - Black Sheep was also New Zealandish. I can think of 2 other films that meet the criteria. Alternate answers exist for a number of others, but I sorta prefer Bunnyman's.
I know that the current responders did a hell of a lot better than I could have without a list of the films in front of me. Congratulations.
And I also liked Killer Klowns. But the best acting in the film was performed by the shadow puppets on the wall.

For 18: Rodan?

Questions from part 2 that have additional answers.

20.      Name 3 genuinely funny films. “Genuinely” is defined as causing you or other watchers to laugh out loud at least 3 times.
Groundhog Day, Army of Darkness, Austin Powers
21.      Which film did you find the most genuinely scary? In very few words, care to say why?
None really.
22.      Biggest waste of time? Please no Folklore – too easy.
Motivational Growth
23.      Iron Giant & Fantastic Planet are my two favorite animated Marathon films. Neither for the quality of the animation. Yours?
Iron Giant hands down.
24.      Name 3 films where dogs play significant roles. And yes, John Carter counts.
I Married A Monster From Outer Space, The Thing, A Boy and His Dog
25.      The first Thon film that I ever saw in a theater was The Mysterians. Yours?
Invasion of the Body Snatchers- original 1961 Costa Rica
26.      Name a film that is the sole representative of a given country. There’s an easy answer, but can you think of anything more obscure?
The Host (South Korea), Lady Terminator (Indonesia), Endhiran (India)
27. ANSWERED.
28.      Eating crow is a catchphrase. Who actually does it? (Well a black bird at least.)
Paul
29.      With the exceptions of Fonda & Weaver, few women act the lead in Thon movies. Name one. A whole Bunch here. Galaxina - Dorothy Stratton, Starcrash - Caroline Munroe, 50 Foot Woman - Allison Hayes, Existenz - Jennifer Jason Leigh,   
30.      ANSWERED
31.      Other classic SF stories form the basis of many movies. Name at least 4 written titles which were changed for the movie version.
Here are a few more.  Monster From Land's End - Navy Versus The Night Monster, The Cosmic Frame - Invasion of the Saucermen, We Can Remember It For You Wholesale -Total Recall, The Shape of Things To Come - Things to Come, The Racer - Death Race 2000
32.      ANSWERED
33.      H. G. Welles films. Name 3. (There were 5.)
More than 5. Things to Come, Invisible Man, Food of the Gods, War of the Worlds, The Time Machine, Island of Lost Souls.
34.      Can you name a film that ends with a total non-sequitur? Hint. One of my favorite films ends with the lead staring at a large ringed planet. Other?
35.      Recently saw Killer Klowns From Outer Space. It contained what I thought was the worst acting ever shown on a movie screen. Not one performance. Every performance. Your nomination for the worst acted Thon film?
Killer Klowns is terrific.  Any Larry Blamire film.
36.      Lots of bug movies: at least 6. Name 4.
Them!, Tarantula, World without End (giant spider), Queen of Outer Space (same spider), Food of the Gods, Five Million Years to Earth, ST 2 (ear bugs), Phase IV, Andromeda Strain (if you want to extend the definition of "bug"), First Men in the Moon, Mysterious Island (giant bees), Tremors (bugs?), The Tingler (a bug?)
37.      One critic said that Plan 9 From Outer Space was the worst film ever made. Name three actors therein.
Gregory Walcott (Eastwood used him in a few films back in the day), Tor Johnson, Conrad Brooks
38.      ANSWERED.
39.      ANSWERED

Thanks for the interest shown. Any additional answers appreciated.
I find it genuinely interesting to learn about others viewing backgrounds and preferences, so please keep posting on the subjective Qs.
And while the caveats about question 18 are legit, it would seem to be difficult to say that anything but MOTHRA!!! had the greatest wingspan.

Okay. Okay. You win.
I suffer from my affections.
As it happens, never saw Giant Claw. Have seen Ghidorah, although it was in Destroy All Monsters.
When I think of Mothra, she seems the epitome of wingspan.
But I did say "Largest." You got it.

one of the funniest was "journey to the center of the earth" sf 11. it was my first experience with a full marathon. it played last and the final scene induced an extended belly laugh from the whole audience. pat boone got shot out of a volcano and landed in a convent with no clothes on. he used a sheep to cover himself.