One thing that makes it special is the creativity of the fans. They can take the existing Supernatural universe and expand it in ways the show might not have. For example, they can create new types of monsters or new backstories for the characters.
Well, 'The Hidden Path' is quite popular. It has a unique take on the Supernatural lore. It focuses on a mystery that the boys have to solve, and there are some really cool twists and turns along the way. It also has some great character development for both Sam and Dean.
I'm not entirely sure who 'Collen' is in the context of Ray Donovan. There could be a misspelling perhaps. If it's about Ray Donovan in general, he's a fixer who has a complex family background and gets involved in all sorts of dirty business in Hollywood to protect his clients.
In a sense, it's not a literal 'watching' as the show is an inanimate creation. But in the context of the show's creators or those associated with it being aware of fanfiction, it can be normal. They might look at it for inspiration or to gauge fan interest.
The main difference is the macrophilia element. Regular Supernatural fanfiction usually sticks to the themes and storylines within the show's framework more closely, like hunting monsters and the relationship between the Winchester brothers. But Supernatural macrophilia fanfiction adds the macrophilia concept, which changes the focus and can lead to very different character interactions and plot developments.
Well, Tumblr can be a great place to search for Supernatural fanfiction. Many fans post links to their favorite fics or even write short ones directly on their blogs. Another option is Wattpad, though the quality can vary more there. Just search for 'Supernatural' in the search bar, and you'll get a bunch of results.
It could imply that the show 'Supernatural' in some way is associated with or has an influence on the fanfiction related to it. Maybe the show's creators or actors are aware of the fanfiction and are 'watching' in the sense of being aware of what the fans are creating in that realm.
Well, in fanfiction related to 'Supernatural', some writers might show their acknowledgement in various ways. For example, they could reference the original show's plotlines and characters in a respectful manner. This can be as simple as using the correct character traits and backstories. It shows that they are aware of the source material and are building on it in their own creative way.
I'm not sure which one is the absolute longest Supernatural fanfiction as there are so many out there. However, you can try searching on large fanfiction platforms like Archive of Our Own. They have a vast collection of Supernatural fanfics and might give you an idea about the really long ones.