The most important difference between the book and the show is that in the book Crowley is the anxious mess and in the show Aziraphale fills that role
Script book SPOILER alert:
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In the script Crowley is more anxious and I love it! Hastur and Ligur get to threaten him more seriously too. He has insomnia and seems to be close to mental breakdown. I also love Tennant’s take on the role, of course and some of the stuff was cut even though it was already shot (like Crowley trying to sleep first on his own bed, then on the floor and in the end on the ceiling!)











