What happened with Fear and Loathing? cause that film turned out perfect.

The film was originally going to be written and directed by Alex Cox, who got the production greenlighted even though his script was shit because the producers were about to lose the option to make the film. Hunter S. Thompson wanted nothing to do with Alex Cox after learning how he intended to direct the film and basically the movie went into development hell. Gilliam came on board after Cox had basically been fired and the film basically almost fell apart because Cox had been such an ass to Thompson who, briefly, had considered no longer participating in anything having to do with the movie because of his negative experience with Cox. Once Gilliam made his own script (which was basically just a very straight interpretation of most of the book) the Screenwriters Guild of America would not allow Cox's name to be taken off the credits even though he had nothing to do with the movie.
It was not an easy film to make. But yes, it turned out very good.

Oh geez..I totally forgot to mention the best part. Cox sued Universal to make sure his name stayed on the credits (even though it probably would have stayed anyway) and that he should get a "Screenwriters fee" even though the movie is based on a fucking book he didn't even write. Gilliam argued that no one should get credit except Thompson (not even Gilliam), but the Writers Guild wouldn't agree. Cox ended up getting his fee and credit anyway. So yeah..Cox actually argued that his script, which is based on a pre-written thing, was so original that it "bore similarities" to the finished product he had nothing to do with.

This is why the "director's cut" (so to speak) of Fear and Loathing has the intro with the PSA about how "no writers were involved in the film."

Sort of a hybrid of Brazil and Idiocracy...