Midnight Express Sequel

According to IMDb, a sequel for Midnight Express was planned, but never materialized.

Plot
The plot would've had Billy Hayes's girlfriend, Susan, taking him to a western place to find Billy's father, as well as going to an imaginary place called Cloud Cuckoo Land, where a unicorn/cat hybrid (UniKitty) lived.

Then, some aliens invaded the world, one of them kidnapping Billy's friends, Susan, Max, Erich, and the other prisoners, and Billy would rescue them.

Why It Was Cancelled

 * 1) Alan Parker went on to direct Fame.
 * 2) Brad Davis went on to star in A Small Circle of Friends and two TV movies.

Results

 * 1) The ideas were later sent over to The Lego Movie (first paragraph) and its upcoming sequel, The Lego Movie 2: The Second Part (second paragraph).
 * 2) In 2016, a documentary named Midnight Return: The Story of Billy Hayes and Turkey was released, acting as a sequel to the 1978 film.