What is the ruling on someone who remembers in their mind a movie or a game that contains disbelief (kufr) in its content, and are they sinful if they deliberately do so while denying that disbelief?

If you deny disbelief and do not believe in it, then you will not be held accountable for what comes to your mind of it, due to the saying of the Prophet, peace and blessings be upon him: "Indeed, Allah has forgiven my nation for whatever their souls whisper to them, as long as they do not act upon it or speak of it." This includes what is intentional and what is unintentional. It is advised that thoughts should be directed towards what benefits one in matters of religion and worldly life.