(A bit of a read, sorry)

Okay so. Charlie being a down-on-his-luck broke artist living out of his car Dies somehow someway suddenly (I'm not gonna lie he's a major downer in the movie so I would Not be that surprised if he khs impulsively. Sorry my opinion) BUT he doesn't move on. Obviously. And I feel that his motivation, rather than mending relationships like Eddie did, would be more centered on his art making an impact on the world-- particularly because of his outright refusal to change anything about Overlord Oppressed Opossum in the movie. I feel like he really wanted something to be said with it (or anything else he creates). And considering in the movie Charlie wasn't staying with relatives or anything, one could assume there's some kind of strained relationship there. Remember this for later.

Anyways his ghost haunts the car which soon gets sold to a Living Eddie, who can see him!! And it turns out Charlie can't move on because there's a comic which he finished but never got the nerve to try and publish before he suddenly/impulsively died, and now he regrets it. And since it's hard to get things published when you're dead, he gets Eddie to help him out.

Long story short blah blah blah it does well and gets published but Charlie still isn't at peace. He can't move on, and That is because of THE STRAINED RELATIONSHIP WITH HIS FAMILY I TOLD YOU TO REMEMBER! Considering Charlie was doing so rough and was so resistant to change his ideas for marketability's sake they got tired of him pursuing art instead of getting a "real job" and cut him off. So Charlie and Eddie track down his family and show them how meaningful his art actually was and how greatly it's impacting people now that it's out in the world and their approval finally gives him the peace he needs to move on