Dreams

Dreams are the funny pictures you see inside your head while you are sleeping. Most of the times they involve sex. Dreams that have an adverse or frightening effect on the dreamer are referred to as nightmares. Oddly, these too are usually about sex. Dreams plays an important role in various forms of fiction, as they provide a convenient vehicle for plot and character exposition, recapping events from previous stories and foreshadowing future events. They may also be used as filler material if a particular script does not meet the required running time for a particular movie or TV episode. This technique is especially useful in the case of soap operas, which has a very regimented block of time with which to chronicle a tale depending upon weekly broadcast schedule and cast availability.

In speculative fiction, dreams can often become a key plot element, and the concept of dreams and their affect (if any) on the waking world has been experimented with since the earliest days of entertainment.

In DC Comics continuity, the entire land of sleep is a mystical dimension referred to as The Dreaming. It is lorded over by the master of dreams, Morpheus of the Endless. Morpheus headquarters himself inside of a towering palace, where he is assisted by various attendants, some of whom were once humans whose spiritual essence has transcended the mortal coil and become avatars within The Dreaming. As the ultimate Oneiromancer, Morpheus has access to the thoughts and imaginations of every creature on the planet capable of Dreaming. His influence even extends to alien cultures, who often see him cloaked in a guise that is more palatable to their culture and expectations.

Nightmares
AGGGGH!!!! Did that scare ya? No? Then clearly someone wasn't doing something correctly. Nightmares are a form of dream that evokes the darker and more primal elements of fear. In fact, there's an ever-growing laundry list of phobias that can manifest themselves in nightmares (including fear of dreaming).

For example, the character of Sarah Connor from the Terminator franchise often suffers from recurring nightmares of the end of the world. In many of these Apocalyptic scenarios, she even dreams of her own death, which is usually exceedingly violent, such as being roasted to ash in the wake of a nuclear bomb or being murdered by a robotic Terminator. Sarah's nightmares have been so extreme that on one occasion, she actually pulled up stakes and moved based solely on the intensity of a particular nightmare.