Unless you want to be murdered by zealous fans, your adaptation of a book/movie/etc. had better keep certain things intact. Sure, you can cut a scene here or tweak a character there, but in the end, Harry Potter still has to defeat Voldemort, and Katniss still has to win the Hunger Games. Deviate from the plan, and fans scream bloody murder.
But not when it comes to video games. Video game makers don't give two shits about canon, even if the game is based on an all-time cinema classic. They'd tack on a different ending to the freaking crucifixion if they thought it'd make the level play better, and nobody cares. So, let's take a moment to celebrate some of the most awesome and/or insane liberties games have taken with famous plots ...
The Empire Strikes Back -- Luke Kicks Vader's Ass (and Isn't His Son)
In the Movie ...
Some of you are too young to remember how goddamn depressing The Empire Strikes Back was when we saw it for the first time. First the Rebels get the shit blown out of their igloo base. Then, despite the fact that Yoda (literally the wisest being in the entire universe) specifically tells him not to, Luke Skywalker zooms across the galaxy to confront Darth Vader in Billy Dee Williams' Colt 45 Sky Fortress and gets about 13 years beaten off of his life.
"What, did an arthritic old man and a midget train you to sword fight? Oh ... right."
Vader chases Luke through the facility, operating his light saber in full-on baseball bat mode and using space magic to throw a bunch of random shit at the young Rebel, until finally cornering Luke at the end of a bridge and chopping his goddamn hand off. Vader then reveals himself to be Luke's supposedly dead Jedi father, to which Luke responds with mewling shrieks of terror-sadness and then leaps into the cavernous pit below. Thanks for coming, kids! The next movie will be out in a few years!
But in the Game ...
When they sat down to make the NES game in the early 1990s, they decided they were going to get rid of all this depressing shit and write the movie Lucas should have made. So, instead of getting tossed around like a child, Luke arrives at Cloud City to greet Darth Vader with a howling explosion of furious ass-whoop. He sprints down the spindly chasm bridge and pummels the Sith Lord like a jazz drummer cracking open a pinata with a pair of nightsticks, until Vader simply collapses under the weight of his own embarrassing failure and falls off the fucking bridge.
He just shit in his robot suit, and now he has to smell it all the way down.
However, the greater departure from the film's storyline comes after Luke beats Vader in 10 seconds like he was late for a meeting. Once Vader is defeated and sent hurtling down the inexplicable sky abyss/twinkling future slide, he delivers this message:
"Next time, Skywalker ... NEXT TIME!"