Which is correct when I have to be accurate in a more
technical content than the example below?

1. What make this film so interesting are its clever
script writing and unorthodox casting.
2. What makes this film so interesting...(same as above)

I guess #1 is correct following the subject-verb agreement
rule, but doesn’t it sound a little strange?

its clever script writing and unorthodox castingだからじゃない？映画の面白さの説明として、複数あげているから、Areを使っているんでしょう。What areでも、What isでもどっちでもいいけど、その後に続く内容によって、動詞を選ぶ必要があるってことでしょう。 　

Thanx for the reply.
I guess my question wasn’t very clear.
When you use "what" as the subject to represent
two or more items, is it absolutely necessary to
follow with a plural form of the verb?
　

そうじゃないですかね。ためしに「What are」と「What is」をググってみるとこんな結果でした。

「What are」
http://www.google.ca/search?hl=en&q=%22What+are%22&btnG=Search&meta=lr%3D

「What is」
http://www.google.ca/search?hl=en&q=%22What+is%22&btnG=Search&meta=lr%3D

Whatの後に続く文章を確認してください。実際の英語の文章を見比べることで、トピ主さんの質問の答えも見つかるんじゃないでしょうか。 　

Number 2 is correct. This sentence actually has a quite simple form--A is B. [What makes this film so interesting]A is [its clever script writing and unorthodox casting]B. The second part, B, acts like a single noun and can take the place of "What" in "What makes this film . . . ." Therefore, "makes" is correct, not "make." 　

私は1だと思うな。

What(複数)→Are→clever script writing and unorthodox casting(複数の理由)
Cleverの前のitsはthis film(単数)のこと。

この場合、Whatは複数なので続くmakeはそれに呼応する形になります。

でも、clever script writing and unorthodox castingを単数と捕らえると2が正しくなります。 　

Thank you res3 and re4.
Res3 san,
I tried your method but it was very difficult to fish
out "what" used as a non-interrogative pronoun. Most
sentences that come up are interrogative.
Res4 san,
Thanks for clarifying this. 　

Yahoo answer(カナダ版)で聞いたら、今のところ10人に6人が1番が正しいと言っています。でも、MakeはMakesだという人がその6人中2人います。面白い質問でした。ありがとうね。

Number 1 is correct; however, the word "make" should be "makes".

Think of it this way:
Clever script writing and unorthodox casting are what make this film so interesting. 　

誤植でした。↑

Number 1 is correct; however, the word "make" should be "makes".

Think of it this way:
Clever script writing and unorthodox casting are what makes this film so interesting. 　

あ、でも・・・こんな答えも。

2 is correct.You are speaking about one interesting film.It has clever script writing and unothodox casting.It would still include the word if rather than are, if the rest of the sentance included even more than the two references.Example = it’s clever writing,unorthodox casting and beautiful scenery.

なんかこの方があっている気がします。回答者全員がネイティブスピーカーとは限りませんが、2が正しいと言っている人は今のところ、11人中5人です。微妙なところなんでしょうね。でも、たぶん2番があっているのかな。 　

Thank you res5 and res7~9.
I’m more confused than ever.
There’s a line in Res9,
"It has clever script writing and unothodox casting."
but still,
"Clever script writing and unorthodox casting ARE what
MAKE this film interesting."
And "what" in my example represents not "it," or the
"film" but those factors that make "it" interesting.

Res7 san,
I tried to find the question in Yahoo Answers Ca., but
couldn’t locate it. Could you please paste the URL of
the question and replies on this page?
Thanx a zillion.
　

ちなみに質問者は私です。回答は12人から得られていますが、みんな確信はないようですねー。でも、2番が確率的に高そうですよ。

http://ca.answers.yahoo.com/question/index;_ylt=Aod5sRojhgvR9kAOf80SnMDpFQx.;_ylv=3?qid=20080407232936AAE2f3L

　

Thanx.
I counted 7 votes for #1 and 6 for #2.
But a few in #1 say it should be "makes"
rather than "make."
"What makes this film so interesting are its clever
script writing and unorthodox casting."
Now, this almost defies gravity in my brain.