In a June 2008 interview with The Guardian, Abel Ferrara, who directed and co-wrote the original Bad Lieutenant (1992), said that finding out his movie was being remade was "a horrible feeling", "like when you get robbed", and that those involved in this remake "should all die in hell". He also wondered how Nicolas Cage "can even have the nerve to play Harvey Keitel", and called screenwriter William M. Finkelstein an idiot. Herzog responded that he had never seen the original and had never heard of Ferrara.
According to the Werner Herzog, 2,400 cans of decaf coffee had to be used to make the water appear to be river water in the jail scene. They first attempted to use a paint, but it proved to be toxic, then the production team used regular coffee, but the actor absorbed it through his skin.
Although being promoted as a remake of Bad Lieutenant (1992) during its early production, director Werner Herzog claims that this is not a remake. He says he has never seen the original and therefore does not consider this movie a remake. Additionally, producers seemed to have added "Bad Lieutenant" to the title in order to get a better marketing. Whether remake, re-imagining, follow-up or none of the aforementioned, both movies are clearly connected by the basic plot of following a drug addicted, violent cop during his encounters with crime and sex.
According to director Werner Herzog in Paul Cronin's interview book, some of the most talked about scenes and images in the film were not in the original screenplay by William M. Finkelstein and added by Herzog in pre-production or sometimes on the spot. This includes the ideas for the scenes at the beginning and the end (aquarium), the 'dancing soul' scene, the inclusion of the iguanas, the alligator lying on the highway run over, McDonagh's monologue about his silver spoon and the scene where he brings it to his girlfriend. Their relationship was originally mostly drug related and sexual, not as romantic as in the final movie. Some scenes of drug use were omitted by Herzog because of his little interest in drug culture. The major change in location from New York, where the screenplay is set. to New Orleans happened because of budget reasons, but also because Herzog wanted it to become a "leading character". All in all, the final movie differs especially in its humorous tone, additional character scenes and poetic moments from the Finkelstein's screenplay.