The line is from Phillip K. Dick’s The Three Stigmata of Palmer Eldritch:
What we have here, he realized, is not an invasion of Earth by Proxmen, beings from another system. Not an invasion by the legions of a pseudo human race. No. It’s Palmer Eldritch who’s everywhere, growing and growing like a mad weed. Is there a point where he’ll burst, grow too much? All the manifestations of Eldritch, all over Terra and Luna and Mars, Palmer puffing up and bursting–pop, pop, POP! Like Shakespeare says, some damn thing about sticking a mere pin in through the armor, and goodbye king.
The Shakespeare passage referenced is one of Richard’s more famous speeches in Richard II (3.2):
No matter where; of comfort no man speak:
Let’s talk of graves, of worms, and epitaphs;
Make dust our paper and with rainy eyes
Write sorrow on the bosom of the earth,
Let’s choose executors and talk of wills:
And yet not so, for what can we bequeath
Save our deposed bodies to the ground?
Our lands, our lives and all are Bolingbroke’s,
And nothing can we call our own but death
And that small model of the barren earth
Which serves as paste and cover to our bones.
For God’s sake, let us sit upon the ground
And tell sad stories of the death of kings;
How some have been deposed; some slain in war,
Some haunted by the ghosts they have deposed;
Some poison’d by their wives: some sleeping kill’d;
All murder’d: for within the hollow crown
That rounds the mortal temples of a king
Keeps Death his court and there the antic sits,
Scoffing his state and grinning at his pomp,
Allowing him a breath, a little scene,
To monarchize, be fear’d and kill with looks,
Infusing him with self and vain conceit,
As if this flesh which walls about our life,
Were brass impregnable, and humour’d thus
Comes at the last and with a little pin
Bores through his castle wall, and farewell king!
Cover your heads and mock not flesh and blood
With solemn reverence: throw away respect,
Tradition, form and ceremonious duty,
For you have but mistook me all this while:
I live with bread like you, feel want,
Taste grief, need friends: subjected thus,
How can you say to me, I am a king?