<s>[INST] Where is the script below from?

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ARTHUR: O Knights of Ni, we have brought you your shrubbery. May we go now?

HEAD KNIGHT: It is a good shrubbery. I like the laurels particularly,... but there is one small problem.

ARTHUR: What is that?

HEAD KNIGHT: We are now... no longer the Knights Who Say 'Ni'.

KNIGHTS OF NI: Ni! Shh!

HEAD KNIGHT: Shh! We are now the Knights Who Say 'Ecky-ecky-ecky-ecky-pikang-zoop-boing-goodem-zu-owly-zhiv'.

RANDOM: Ni!

HEAD KNIGHT: Therefore, we must give you a test.

ARTHUR: What is this test, O Knights of-- knights who till recently said 'ni'?

HEAD KNIGHT: Firstly, you must find... another shrubbery!

[dramatic chord]

ARTHUR: Not another shrubbery!

RANDOM: Ni!

HEAD KNIGHT: Then, when you have found the shrubbery, you must place it here beside this shrubbery, only slightly higher so you get the two-level effect with a little path running down the middle.

KNIGHTS OF NI: A path! A path! A path! Ni! Shh! Knights of Ni! Ni! Ni! Shh! Shh!...

HEAD KNIGHT: Then, when you have found the shrubbery, you must cut down the mightiest tree in the forest... with... a herring!

[dramatic chord]

KNIGHTS OF NI: A herring!

ARTHUR: We shall do no such thing!

HEAD KNIGHT: Oh, please!

ARTHUR: Cut down a tree with a herring? It can't be done.

KNIGHTS OF NI: Aaaaugh! Aaaugh!

HEAD KNIGHT: Augh! Ohh! Don't say that word.

ARTHUR: What word?

HEAD KNIGHT: I cannot tell, suffice to say is one of the words the Knights of Ni cannot hear.

ARTHUR: How can we not say the word if you don't tell us what it is?

KNIGHTS OF NI: Aaaaugh!

HEAD KNIGHT: You said it again!

ARTHUR: What, 'is'?

KNIGHTS OF NI: Agh! No, not 'is'.

HEAD KNIGHT: No, not 'is'. You wouldn't get vary far in life not saying 'is'.

KNIGHTS OF NI: No, not 'is'. Not 'is'.

BEDEVERE: My liege, it's Sir Robin! [/INST] The script you reference is from the classic 1975 film titled: Monty Python and the Holy Grail. 
Many Monte Python films consisted of loosely connected skits, frequently veiling an underlying theme.

In this case, the Knights Who Say "Ni!", also called the Knights of Ni, is one of the more famous segments of the film.

The reference to a "Shrubbery" has long and storied retelling in many different social circles.</s>\ <s>[INST] Who played the character of the head knight? List a few of other movies he also took part in. [/INST] The character of the head knight in Monty Python and the Holy Grail was played by actor John Cleese. He is a founding member of the Monty Python troupe, and is considered one of the most important members of the group. He co-wrote, acted in, and directed many of the troupe's projects, including Monty Python's Flying Circus and Monty Python and the Holy Grail.
Cleese has also starred in a multitude of other popular films, including A Fish Called Wanda, The World Is Not Enough, Rat Race, Harry Potter and the Deathly Hallows, and the Shrek film series.</s>