Consider this a call to watch tv shows that have nothing to do with your main concept. There is a lot to gain for writers who write “serious” works to watch “unserious” shows. I’ve told this to a couple people already and they all seem to agree with me.
Motivations: Giving your characters a motivation beyond “defeat the latest bad guy” makes your job easier! Alongside a long-term goal, like “scam the neighborhood kids out of their money to afford giant jawbreakers”, you give your characters core motivations like “have fun at every turn”, “a fool and his money are soon parted so what is the harm in parting them?”, and “make sure that we don’t get caught or killed”. If I had the choice, I’d much rather write for Ed, Edd, n Eddy because you can come up with plots far more easily than Supernatural after a few seasons, though part of that might just be because the antagonists aren’t constantly replaced.
Don’t be afraid to give your characters less-than-noble motivations, it makes them more real.
Personality: Always go for a strong, easy to understand personality, at least to start with. Add depth over time, of course, but something strong and easy to grasp is better for your audience, actors, and writers to “get” a character’s deal.
Diversity: The fact that a Cartoon Network show released in 1998 has a more diverse supporting cast than Tumblr’s favorite demon-hunting show is a depressing fact that says a lot about the society we live in. Not everyone save for your main characters should get killed off-returning characters can have great stories and you have options other than death to write a character out of a story.
It’s Funny: Well, duh, CW shows are rarely funny, and when they are, it’s always accidentally. In the words of The Joker, the second-best Batman villain “Why so serious?”
Imagining Dean saying “Dig a hole, dig a hole” makes everyone smile.
The only possible option for Eddy that I can tell is probably John Winchester but I am not certain.