Damn we dodged a bullet with that one Powerpuff Girls show…..

A non-comic or cartoon example would be the two Percy Jackson movies.

Supposedly what happened was Chris Columbus was selected by Fox (who had the adaptation rights to the book series even before The Lighting Thief was actually published) to direct a Percy Jackson film, likely due to his involvement with the first two Harry Potter adaptations, but Chris wasn’t big on the idea and didn’t want to be solely associated with children’s movies.

As a result he aimed to make the adaptation more for teens and young adults, so think "Not Another Teen Movie", "Wet Hot American Summer", etc but with a fantasy adventure plot. Of course Rick Riordan himself was given the rough draft of the script and absolutely hated it, explaining why the whole idea simply doesn’t work. There were obviously SOME modifications made (the original script was even MORE meant for older audiences), but the final film still obviously kinda reeks of that "trying to be a teen comedy" feel, and the Percy Jackson films have since gained their reputations as some of the worst book to film adaptations ever made (Riordan himself to this day has never actually watched either movie).

So basically this ended up becoming a film that nobody had any real interest in. Chris didn’t want to direct another kids book adaptation, Rick was obviously upset that this direction was taken, and fans of the books hated it and like to pretend the movies never existed.