so. I do think it's quite possible that Crowley was formerly the archangel known as Lucifer and I've written about how the narrative so far supports this theory (or at least hasn't jossed it yet) already.
I want to clarify what I really mean when I say "I think Crowley was Lucifer before he Fell". I think he was the angel humanity sometimes calls Lucifer.
First, here's the wiki on Lucifer. It's not a traditional angel name, but actually a Latin word for "the one who brings light". Lucifer has been both synonymous and separate from Satan, Beelzebub, and the Devil - humanity just can't decide or agree who this tricky one is!
As a former catholic school girl with years of qualifying religious trauma, I can say that I only know of one mention of the name Lucifer in the Bible, and it's something like "Lucifer, oh fallen angel, the morning star who struck the ground blah blah" whatever. In Revelation Jesus actually calls himself the "morning star" which is... funny in this context.
So not a lot of bible canon to go off. We could look at Milton, or Dante, or literally any other intentionally fictitious stuff about Lucifer to look for Clues!, but honestly? I think that's kinda pointless. I think only Good Omens canon matters.
And we've gotten exactly one name drop of Lucifer so far. By Crowley. While he's wasted, thinks Aziraphale is dead, and is waiting for the world to end. He's talking about his Fall. He says:
"I was just minding my own business one day, and then it's 'oh look here it's Lucifer and the guys'."
It's ambiguous if he's referring to himself or someone else.
But really, I'm not super interested in that, either. What's in a name, right? Crowley changes his all the time.
I don't think it matters if Crowley's Name was Lucifer. What I'm interested in is if Crowley is the fallen angel that humanity sometimes calls Lucifer. The things we sometimes attribute to Lucifer in western culture include: being the serpent of Eden, tempting Christ in the desert with the kingdoms of the world, and causing a third of all angels to Fall by challenging the authority of god.
I think Crowley was the other Prince of Heaven mentioned in s2. I think he was the former Supreme Archangel of Heaven. I think he was the/one of the Morningstars. I think he was God's first angel.
Aside from the scene where we see him literally creating the heavens (flowery archaic term for the cosmos), Crowley says he worked closely with "upstairs" on the design. He seems confident enough in his relationship with god to question her. He makes the statement "if I was running things" which is... hugely blasphemous and definitely something humanity has attributed to the fallen angel we sometimes call Lucifer.
I don't really think Crowley's angel name will ever be revealed, tbh? But I think enough about him and his former angelic identity will be revealed that we'll know. I think names, especially Crowley's, are super important in Good Omens as signifiers of identity, and Crowley's whole existence, the Point of him, is about casting off the identities others put on you, and forging your own.
Who cares what his name was? I wanna know why he's so certain that Aziraphale won't be able to make a single bit of difference by going back to Heaven, even as the Supreme Archangel. I wanna know why Crowley could access those high clearance files, why the actual archangels followed him around, listened to him, and seemed to give him a weird measure of respect, why Shax called him "arch-traitor", why he said "I know" when Gabriel said it hurt to try to remember, why he and the Metatron did That look, why he's so different from all the other demons and angels. What's the story there? What's he hiding from Aziraphale when he chooses not to tell him about any of this? Why does he give different accounts and reasons for his Fall? What's his secret shame, besties?
I think Crowley was the angel who inadvertently triggered a rebellion by asking too many of the "wrong" kinds of questions. I think he thinks he's responsible for the First War, and for the Fall, and by extension, for the different Sides.