In some fanfictions, Lucifer might be punished by being trapped in a desolate dimension. This is often a way for the writers to show that even a powerful being like him can't escape justice. For Crowley, he could be punished by losing his demonic powers. It makes sense as his powers are a big part of what makes him a threat in the Supernatural universe.
In some fanfictions, Lucifer's punishment is shown as being bound to a mortal body and experiencing all the pain and frailty that comes with it. For Crowley, his punishment may be that he has to constantly watch his carefully built demonic empire crumble around him. It's a cruel punishment for a character who values power and control so much. The writers use these punishments to explore different aspects of their characters and how they would react in such extreme situations.
Well, the dog could be a messenger. For example, it could be sent by some higher power to warn Crowley about Lucifer's upcoming plans. It might have a special mark or ability that makes it stand out. Like it can run between different realms where normal creatures can't, and it uses this ability to keep tabs on Lucifer and report back to Crowley.
A possible fanfiction idea is that the dog is a reincarnation of an ancient being that has a connection to both Lucifer and Crowley. In the past, this being was involved in a great battle between good and evil. Now, as a dog, it has no memory of its past. Lucifer wants to use the dog to regain his former glory, while Crowley wants to keep the dog away from Lucifer to maintain the balance of power. The story could follow the dog's journey as it discovers its true identity and has to make a choice between the two powerful forces.
Yes, there are some. Some fanfictions focus on how Crowley's loyalty to Lucifer is tested in situations that involve shame. For instance, when Lucifer asks Crowley to perform tasks that go against Crowley's new - found sense of self in the series.
Definitely Sam and Dean Winchester. They are the main protagonists in 'Supernatural' and have a long - standing feud with Lucifer. They've fought him numerous times and would be the most likely to be involved in his punishment. Their motivation would be to protect the world from Lucifer's evil plans.
Well, I really like the fanfic 'Crowley's Secret Alliances'. It shows Crowley forming unexpected partnerships in the Supernatural world. There's also 'A Day in the Life of Crowley' which gives a really in - depth look at his daily activities. And don't forget 'Crowley vs. the Archangels', it has some great action scenes involving Crowley.
One could be a fanfic where Lucifer tries to manipulate Crowley into doing something shameful for his own gain. Maybe Lucifer convinces Crowley to betray a mutual acquaintance in a way that makes Crowley feel ashamed of himself later.
A really popular one is 'Lucifer and Crowley: A New World'. In this fanfic, they find themselves in a completely new world, perhaps a parallel universe. They have to figure out how to survive and also how their relationship changes in this new and strange environment. It has a lot of action and adventure elements as they encounter new threats and opportunities.
One possible fanfiction idea could be that Crowley's daughter is half - human and she struggles with her demonic heritage. She might try to find a way to be different from her father and his cruel ways in the Supernatural world.