Crowley adjusted his shades and shoved a cassette into the Bentley's tape player. He was angry. Not at Aziraphale exclusively, but at the whole world. And considering what had happened the last time he drank, he took to the Bentley for comfort. For a while he just drove aimlessly, but for a solid hour now he had simply driven around the same roundabout at 90 mph, never leaving, just driving around and around and generally pissing people off.
He was feeling better already.
The cassette started. "Ooh, you make me live... You're my best fri-ee-end..." Annoyed, Crowley hit the eject button. Even the radio was preferable to this.
A commercial for plate-glass windows ended and and a simple guitar melody floated through the speakers. A very familiar, very cheerful guitar. "And I wonder... Are you thinking of me? 'Cause I'm thinking of you..." Oh no. BBMak. Crowley scowled, fervently wishing he had never thought of boy bands, and turned off the knob. Behind him several angry drivers honked their horns, and the demon smiled humorlessly.
Mythology, unlike Betamacks, Pauly Shore, or bellbottomed pants, has more or less been around since civilization began. Four thousand years later, and the old stories are as well-preserved as when Greek women sat around the temple praying to Demeter. The attitude has changed since then, however -- unlike when it originated, today the general consensus seems to be that the stories are just that -- stories. A load of tosh some imaginative Mediterranean man made up one day to explain the state of the universe. And if it wasn't -- well, then they had been praying to the wrong god.
They were half-right in these assumptions. They most certainly had been praying to the correct god, but very few people were aware that mythology was a compilation of translations for events that had actually occurred. And Zeus? An angel, one of the higher-ups, who had merely gotten a bit too curious about certain human practices and had decided to try them out. All that jazz with the lightning? Simply sparks from his flaming sword, which he used to impress mortal women. The actual mythology came later, when he got inventive. In all truth, the stories were merely creative versions of things that had occurred amongst the otherworldly elite, but the humans wouldn't know that. In most of the stories, the different characters were actually members of his own family (1).
Eventually Metatron became aware of what Zeus was doing -- though, thankfully, he never realized he was part of the mythology as well, or there would have been an almighty scuffle. As it was God let him off lightly, considering that Zeus was immensely popular and had turned an entire climate zone onto religion (2). In the end Zeus was firmly ordered to live on Earth permanently, without any further canoodling with mortal women. If he was caught in another of these liaisons, he would surely Fall.
Saying that Zeus was an abnormally cocky person is like saying Emily Dickinson was an abnormally shy person. Forty-two hundred and seventy-two years later, a son was born.
Zeus Fell, and hard. Most of those in Heaven blamed the child for all this, and he was ostracized by the majority of his angelic family. That is, except for his third cousin, who had spent an extraordinarily long time on Earth and had grown used to their strange charm; in their fondness for humans they were linked, however weakly.
At the moment it was the day after Crowley stormed out, a fact Aziraphale was trying not to think about as he tidied up the bookshelves. He was dusting off his copy of Walden when the bell chimed above the door, and he found the son of Zeus standing in his shop.
(1) His second cousin Aziraphale, for example, was represented by Prometheus, who gave the gift of fire to mankind. The bit about having his liver pecked out every day for eternity Aziraphale did not find amusing, but Zeus claimed he was tipsy when that bit came about and it just happened to stick. This is just one of the reasons that Aziraphale has never felt all that inclined towards his cousin.
(2) As for Zeus inexplicably being represented as the major god in these stories, the angel insisted that he had nothing to do with it and that it had been the Greeks' reverence that had caused it. God, on his part, remained skeptical but was feeling benevolent that day and decided to let it slide.