The film was never finished, and was released as a work in progress when the studio decided to move up the release date and release the film as it was, telling director Joe Dante that he was finished and they were going to go ahead and release what he had at that point.
The actual computer that was used to make the screen display for Wolfgang's computer was not an Apple IIc, it was an SGI Iris 1400 Workstation that cost $35,000. It contained a 73 megabyte hard drive, 1.5 megabytes of memory, weighed 130 lbs and required a custom portable wooden crate to house it on set. The movie needed a program written in C language that could redraw a 3D wire-frame scene in real-time, a feat not possible before SGI produced this specialized hardware. The movement of the energy sphere on screen was controlled by a mouse and happened in real-time for each scene and take, in response to the director's instructions. The workstation was modified to synchronize with the motion picture camera (to eliminate flicker) by tapping into one of the circuit boards. The workstation had no windows operating system: all programs were controlled with Unix commands.
When the helicopter pilot looks at the newspaper, one of the headlines says "Kingston Falls 'Riot' Still Unexplained". Kingston Falls was the town where the events in Gremlins (1984) (also directed by Joe Dante), took place.
River Phoenix, who had grown up in communes in South America, was somewhat unfamiliar with popular culture and slang words. During rehearsals it became a running joke when he would attempt scripted well-known words and phrases and usually pronounce them incorrectly.
At one point, the boys are watching at the Drive-In a movie featuring a spacefaring hero named Starkiller. George Lucas originally intended the lead character of his movie Star Wars: Episode IV - A New Hope (1977) to be called Luke Starkiller until he changed it to Skywalker at the last minute.
Robert Picardo says the alien makeup is the most uncomfortable he has ever worn. The Wak makeup was like having a typewriter balanced on his head and the father was like balancing a TV. Whilst the crew where enjoying lunch he would have to sit there and take the pain which drew him to tears and actually caused open lesions on his head.
Originally the film was going to be directed by Wolfgang Petersen, who wanted to film it in Germany. The studio balked at this decision. Petersen would instead go on to direct the 1985 science fiction film, Enemy Mine (1985), which was filmed in Germany and released by 20th Century Fox later that year.
There are numerous references to Looney Tunes cartoons throughout. When the boys create the sphere in Wolfgang's basement and it goes crashing out a window, the imprint in the glass looks suspiciously like Bugs Bunny's head. Also, Wak's first words to Ben and Darren are "What's up Doc?".
Wak can be heard uttering a line of dialogue from The Maltese Falcon (1941) in response to Darren's question about the crystal gift given at the end of the film. The line is "The uhh... stuff that dreams are made of."
The computer Wolfgang uses to control the bubble and eventually the completed spacecraft is an Apple IIc, a computer released by Apple in April 1984 that sported a blazingly fast 1.4MHz processor and 128 kilobytes of RAM.
Both Wolfgang and Ben have extensive sci-fi literature in their houses. Here are the titles of the books that can be recognized: 1) The Stars My Destination - Alfred Bester, 2) Childhoo's End - Arthur C Clark, 3) The End of Eternity - Isaac Asimov, 4) Starmother - Sydney J. Van Scyoc 5) Midsummer Century - James Blish 6) The Twilight of Briarers - Richard Cowper, 7) Stargate - Andre Norton, 8) Mindbridge - Joe Haldeman, 9) The Overlords of War - Gerard Klein and 10) Doc Savage - Kenneth Robeson (seen on Wolfgang's nightstand).
Dick Miller was in this movie and Gremlins (1984) which this movie references through the newspaper his copilot (Meshach Taylor) picks up after spotting the UFO which reads "Kingston Falls 'Riot' Still Unexplained" (which is the town in Gremlins takes place).