Arc Fatigue: To its limited credit, the movie skipped the chapters involving the long search for radiation and the actual gold mining.
Critic-Proof: It overcame mixed-to-negative reviews to reach the top of The New York Times' bestseller list, though bulk-buying by Scientologists was alleged to have played a part.
Ending Fatigue: The book's climax is around page 320, and there's an obvious enough ending (or a point where it could have been split into two books) when the humans have retaken their planet. And then the book keeps going for 700 more pages.
Inferred Holocaust: Some of the Psychlo bases on other worlds were in the middle of occupied cities. When Jonnie checks on them a year or so after his attack on the Psychlo Empire, he finds blasted, lifeless ruins.
Squick: The Bittie and Pattie relationship. If we're optimistic and they're both about the same age, we have two eight-year-olds who decide to get married someday. Then Bittie dies, and Pattie goes into a deep depression. And then years pass and Pattie still hasn't moved on, goes to Bittie's tomb, and demands that a parson marry them.
Adaptation Displacement: And to most viewers, for the worse. While the book was a bestseller in its day, it sold to a very niche audience. The film was intended to be a mass audience-pleasing blockbuster, and it is safe to say it failed to achieve that goal.
Alternative Character Interpretation: The Psychlos are so stupid and childish, it seems impossible they could have ever built their civilisation without destroying themselves with their petty infighting. It makes a lot more sense if one imagines that Psychlos were themselves a race of backward slaves whose masters invaded Earth a millennium before, but died out for some unexplained reason(s) during the interim, leaving behind all their technology for the Psychlos to abuse. Using gas-drones allow them to move in and destroy the local population without having a Psychlo brain screwing it up.
Awesome Music: Elia Cmíral's score is one of the few good things about the movie. A selection of examples:
The aptly named "Battlefield Earth Theme", which plays over the opening zoom-in to Earth and pan through the Rocky Mountains;
“Psychlo Wrangler”, which plays under a Psychlo hunting Jonnie, Carlo, and Rock in the mall;
The double whammy of "The Dome" and “Terl”, which underscores Jonnie's trip to the human processing center, shooting of the wrangler, and our introduction to Terl;
“The Cavalry”/“Air Battle”, which underscores Robert the Fox’s Big Damn Heroes moment in the Harrier and his and his men’s ensuing dogfight with Psychlo battlecraft;
Big-Lipped Alligator Moment: The "plot" is so nonsensical and poorly constructed that very few of the Psychlos' scenes seem to flow logically into one another, but the hysterically "dramatic" water hose scene, where a few bored-looking Psychlos spray water on human cavemen, who thrash around like they're being sprayed with acid and slap ineffectually at the Psychlos, is bad even for this plot. This goes on for about a minute, and then the movie just kind of awkwardly moves on like it's embarrassed by what it just showed to the audience. Some critics posited that the scene was intended as a Shout-Out to the “It’s a madhouse!” scene from Planet of the Apes (1968), but it’s shot in a way that completely loses the homage.
Bile Fascination: The movie regularly places in the top (bottom?) ten of many "worst movies of all time" lists made by critics and casual viewers alike.
Complete Monster: Terl is the Psychlo head of security on Earth. Running inhumane camps where "Man-Animals" are enslaved, brutalized, and exterminated, Terl holds to hope he can destroy Earth in leaving it to return to Psychlo. Thanks to his indiscretions destroying his hopes of advancement and fleeing Earth, Terl initiates a scheme to force the hero Jonnie to mine illegal gold for him to bribe his way home. Planning on liquidating his workers after constantly lording his supremacy over humans, Terl later tries to have them killed and even attempts to detonate an explosive collar on Jonnie's girlfriend out of spite. He also attempts to kill the entire human population with a gas drone.
Delusion Conclusion: One might guess that the ending is Johnnie's Dying Dream as he succumbs to lack of oxygen after venturing outside the city dome.
Ensemble Dark Horse: Ker for being the Only Sane Man amongst the Psychlos. Forest Whitaker's performance of often expressing disgust or frustration with the very same things the audience would endeared him to many viewers.
Travolta's "While you were still learning to spell your name!" line is funny if you look at his infamous mispronunciation of Idina Menzel's name at the 86th Oscars.
One of Terl's lines in the infamous cow scene is "I graduated top marksman in my class and I can kill any one of you at over a thousand paces", which is nearly a verbatim quotation of a line from the memetic Navy Seal Copypasta.
Ho Yay: One of Jonnie's followers spends much of the movie looking soulfully at his leader. Jonnie even cuts off a lock of his hair for him, and he wraps it around his fist as a sort of talisman. Arguably, Jonnie has more chemistry with this guy than with his designated love interest. The RiffTrax guys had no trouble picking up on this subtext. Whenever the guy makes puppy dog eyes at Jonnie, they start tearfully muttering "Love you!"
Love to Hate: Terl is quite the slimebag and is a total moron, but he is also incredibly entertaining, albeit for the wrong reasons.
Given all the tilted camera shots in this movie, refraining from watching it is probably a good idea if you suffer from motion sickness.
The entire film seems bent on making the viewers as queasy and uncomfortable as possible. From the dirty, grimy actors and environments, to the physically repulsive Psychlos (of both sexes) and ridiculous costume design. Not to mention the overly-harsh filters, making everything too blue, or too green, or whatever. This may have been the point, but that's little consolation.
Protection from Editors: One of the most unusual examples of such ever. Reportedly, because L. Ron Hubbard wrote the original novel, it's effectively regarded as a holy text by the Church of Scientology, and so if the movie deviated too much from the novel (save a few minor details such as Fort Knox still having gold in it), Travolta would have been severely punished and possibly even expelled from the organization.
So Bad, It's Good: A lot of people called it the greatest unintentionally hilarious sci-fi movie ever made. If you can get past the Nausea Fuel, it can almost pass for an incredible comedy.
One of the most infamous examples is when Terl demonstrates his weapon to his human workers by shooting the leg off a cow. It's clear that when Terl does this it's just a concealed string pulling the leg off a model cow.
The laser gun effects demonstrated during the Psychlos' first appearance would barely be passable in a laser tag game.
The Psychlos seem to vary between having six fingers or the normal five. To be fair, in the book they had five fingers on one hand and six on the other. This still doesn't explain the number of figures on the same hand changing from scene to scene.
At one point, a hologram of a Clinko instructs Jonnie. Even though the projection sort of conceals it, it is clear how fake the CGI used for this alien is.
Tear Jerker: The deaths of Carlo and Mickey, mainly because Kim Coates and Christian Tessier manage to make them likable in spite of the thin material they had to work with.
They Wasted a Perfectly Good Character: Zete is the highest-ranked Psychlo in the film, connected to both a "home office" which runs the Psychlo empire as a corporation and at least one (unseen) senator who represents the empire's politicians. He gets one scene and all he does is notify Terl that his assignment on Earth has been extended.
John Travolta. Arguably subverted, though — he was so confident in the film that he was either trying too hard or not really trying.
Just about everyone plays it straight. Even the Psychlos, who come from a World of Ham, seem to take their ham very seriously. Only Forest Whitaker seems to be having fun with his role, and he said later that he did the role only for Money, Dear Boy but even later came to regret that.
Visual Effects of Awesome: While the CGI is generally mediocre at best, the collapse of the Psychlo dome and the resulting destruction of much of Denver (which, unlike most of the film's other effects, was achieved with physical models) is surprisingly great.
The Psychlos have large, prominent elongated heads and dreadlocks, with enhanced codpieces and claws among other things. And that says nothing of those ridiculous jumpsuits...
The Psychlos' means of breathing in Earth's oxygen-rich atmosphere? Sticking rubber hoses up their noses. Made even funnier by Travolta's Catchphrase in Welcome Back, Kotter.
The Planetship, with his exaggerated chin, also stands out as such.
"Battlefield Earth Theme", which plays over the opening zoom-in to Earth and pan through the Rocky Mountains;