Luke Skywalker did not fight Darth Vader on the Jawa sandcrawler! Nor did he rescue Obi-Wan Kenobi from the Egyptian-themed planet of Kessel. Yet both these things occur, in flagrant violation of Star Wars continuity, in Namco's Famicom game Star Wars.
Luke Skywalker's undewater battle with Darth Vader
We shouldn't judge Star Wars too harshly. The protocols for creating a video game based on a feature film were not not fully formed in 1987. Earlier titles, such Star Wars, the arcade game, and Tron were content to recreate certain action packed moments from those films, without any thought to plot or characterization. E.T. tried to cram bits and pieces of that blockbuster in the confines of a typical 2600 game. The result was a game based themes and imagery from the movie, but would make no sense to anyone not already familiar with the film. Others, such as the Master System Rambo or Top Gun, simply took the name and crammed into an existing video game genre; these games make no attempt to recreate the plot of Rambo or Top Gun.
Not an exact quote from the film
Star Wars and Pack-in-Video's Rambo both take the films' plots as their basic starting point. Namco's game begins with a recreation of Star Wars' opening title scroll and space combat scene. The intent is clearly to let the player know you are playing "Star Wars", but in video game form. Luke finds the message from Leia, boards the Millennium Falcon and is taken aboard the Death Star. At various points, you are obligated to engage in dog fights with Tie Fighters. So far, this all sounds very faithful to the original movie; but Namco -- perhaps feeling Star Wars' plot did not have enough opportunities for side-scrolling platfomer action -- felt the need to greatly embellish the story. Now Luke also travels to an ice world, and underwater world, and so on, in order to rescue his compatriots. Certainly, these levels each need a boss. Who else would do but Darth Vader himself? This leads to various oddites; Luke does not encounter Han Solo until near the game's end, but has been cruising around in the Millennium Falcon the entire time.
Rambo faces down the child-kidnapping giant spider
Pack-in-Video's Rambo finds itself in a similar situation. There had been earlier games based on Rambo: First Blood Part II, including those for western PCs, Japanese PCs, and the SMS. But the NES/Famicom title was the first to attempt to recreate the movie's plot, though along the way, the storyline goes completely off the rails. Your John Rambo sprite interacts with Co, Trautman and Murdock, and even quotes lines from the movie. Yet somehow you find Rambo knifing bees, flamingos, gorillas, flying skulls, and strange, invisible humanoid creatures. The game's first boss is a giant spider and Rambo turns Murdock into a frog at one point.
The power of IKARI!
We really can't fault Namco and Pack-in for all this nonsense. In 2009, our first instinct upon playing Rambo is to resort to snark: "Gee, I guess I must have slept through the scene where Rambo fights bats and fireball spitting plants in a cave." But at the time these games were released, there were no "rules" for movie-inspired video games stating what could and couldn't be done. Nowadays, the studios undoubtedly have a lot of editorial control over the contents of such games*; God knows we wouldn't want a Star Wars game straying too far from canon. But in 1987, the expectations were simply that characters and locations from the movie would appear in the game. No one said that a mere video game had to faithful to the movie.
*LJN's Karate Kid and Jaws stayed reasonably close to events in the films. Of course, LJN was owned by MCA/Universal. Later, Lucasarts' series of Star Wars games would promote the idea that games should be integrated into the world of the movies.