Julius and Vincent Benedict are fraternal twins; the results of a secret experiment carried out at a genetics laboratory to produce the perfect child, using sperm donated by six different fathers. The mother was told that the children died at birth, while the children were informed once old enough that their mother died in childbirth. The program was a success but was shut down, due to one twin inheriting the "desirable traits", and the other being the "genetic trash": Julius is strong, handsome, kind and intelligent, while Vincent is, well, Danny DeVito.
The two meet when they're both 35 and Julius bails Vincent out of jail. Vincent doesn't warm up to Julius right away, but he soon does.
Vincent steals a car that happens to have a secret prototype fuel injector worth five million dollars in the trunk. He is going to drive to Houston to sell it for money he owes to loan sharks, but Julius finds out that their mother is really alive and they might be able to find her, and the drive to Houston soon turns into a road trip with Vincent, Julius, Vincent's girlfriend Linda and Linda's sister Marnie. They are pursued by Webster, the criminal responsible for transporting the fuel injector. Hilarity Ensues.
This film provides examples of:
- Actor Allusion: Julius tells Dr. Traven that if he's lying, "I'll be back".
- Adorkable: Julius, especially on the topic of women.
- Badass Adorable: Julius is an interesting example; he is adorable not because of his appearance, but because of his gentle, innocent and kind-hearted personality.
- Babies Ever After: At the end, lo and behold, the twins have married the twins and have each had... twins.
- Bait-and-Switch: In the last scene, when the mother notes "I just can't get over how alike they are", the camera cuts to Julius and Vincent but then pans down to the twin babies in the buggies.
- Bedroom Adultery Scene: Vincent's introductory scene.
- Berserk Button: Vincent finds out the hard way that calling Burt Klane a "blimp" isn't the smartest thing to do.
- Beware the Nice Ones: Julius. He doesn't want to hurt you; that doesn't mean he can't.
- Big Brother Instinct: Julius develops this immediately.
- Big Guy, Little Guy: And it's rather hard to get them mixed up.
- Blatant Lies: Dr. Mitchell Traven denied any knowledge of the program. ("I don't know who you are, and I don't know what you're talking about!") This pissed Julius off.
- Bond One-Liner: During the final confrontation, once the chains finally finish piling up on the villain, Vincent looks in mild shock before delivering "Now there's a guy with a lot on his mind."
- But I Read a Book About It: Julius knew all about driving from reading about it, and having read the car's manual, he knew he could shut off the alarm by lifting it up from the back, thereby tricking it into thinking it was being towed. Of course it only worked because of his extraordinary strength.
- Car Skiing: Julius does one of these completely by accident his first time driving a car.Julius: Maybe I can teach you that sometime.
Vincent: Julius, let me give you a little advice: here in America, nobody likes a smartass.
- Cassandra Truth: No one ever believes that Vincent and Julius are twins. Vincent doesn't even believe it until about halfway through the film.
- Coat Over the Shoulder: Vincent gets them matching sets of cool white suits. They simultaneously flip their jackets, with Julius's jacket floating over Vincent.
- Conscience Makes You Go Back: Julius makes Vincent grow a conscience, which irritates Vincent to no end.Julius: Why did you come back?
Vincent: Why? I'll tell you why, it's because I have a disease called a conscience.
Julius: No one said doing the right thing was easy.
Vincent: "No one said doing the right thing was easy."
- Curb-Stomp Battle: Julius' fight with the Klane heavy in Vincent's office. Later he easily dispatches four of them in the nightclub.
- The Cynic: Vincent has had one too many disappointments in his life to believe in concepts like love, kindness and hope.
- Designer Babies: Julius and Vincent are the results of a secret experiment carried out at a U.S. Government genetics laboratory to produce the perfect child. To the surprise of the scientists, the embryo split and twins were born. One twin, Julius, is seemingly "perfect", exhibiting all the traits the scientists were hoping to achieve, while the other, Vincent, is much more "average", to the scientists' dismay.Mitchell Traven: The embryo did split in two, but it didn't split equally. All the purity and strength went into Julius. All the crap that was left over went into what you see in the mirror every morning.
- Double In-Law Marriage: The end has the twins marrying sisters.
- Dr. Jerk: Dr. Mitchell Traven at best, bordering on Morally Ambiguous Doctorate. It's not possible to justify breaking up a family the way he did, no matter what his reasons for it.
- Even Bad Men Love Their Mamas: Vincent, at least when he finds out he was lied to when told he was a Son of a Whore. Of course, by the time he and his true mother meet, he's not really that bad anymore.
- Expecting Someone Taller: When Julius visits Vincent in jail, his reaction eyeing on a tall burly man walking by before Vincent sit across him and thought he got the wrong person.
- Flat "What": Vincent's reaction when Julius told him he's his brother.
- Genius Bruiser: Julius.
- Gentle Giant: Keep in mind that this role was very much Playing Against Type for Arnie at first, since he was then-known either as an action hero or The Terminator.
- Grand Romantic Gesture: Vincent has his love interest's room decorated with flowers. She is floored.
- The Grovel: Towards the end during his Grand Romantic Gesture, Vincent is on his knees begging his love interest for forgiveness. It works.
- Has Two Mommies: How many fathers do the twins have?
- Hawaiian-Shirted Tourist: The two couriers who deliver the car to the garage try to pass themselves off as tourists by wearing Hawaiian shirts.
- Hero Stole My Bike: Julius jacks a convertible with buffalo horns on the hood in Twins, but later mentions that he returned it.
- Hot for Teacher: Vincent somehow managed to seduce Sister Maria, one of the nuns who was his biology teacher at the orphanage where he grew up. This resulted in Sister Maria losing her job before he ran away.
- Hypocrite: Vincent accuses Linda of accompanying him on the journey because her interests were only financial, even though five million dollars is exactly what motivated his road trip in the first place. Though he likely just taking his anger on the news of his mother's supposed death on her.
- Informed Ability: Some of Julius' abilities, like his superior skill at math. Justified in that only some of his skills are relevant to the plot, and usually only for a single scene each.
- In the Blood: Done in a more controlled and planned manner than usual. Dr. Traven and his team took sperm from men who excelled in all fields — a Nobel Prize-winning scientist, a bodybuilder etc. so they could create someone who was literally a master at everything. The embryo's split into a "good" twin and a "bad" twin in Mary-Ann's womb, however, was not planned for.
- Jerkass: Mitchell Traven. He treats Vincent like crap, because his unexpected birth was the reason the program was shut down. Also because of it, he told Mary Ann, their birth mother, that her child died at birth.
- Jerk with a Heart of Gold: Vincent, after some Character Development.
- Kavorka Man: Vincent. Prior to meeting Julius, he doesn't have many redeeming features but nevertheless seems to have had no trouble attracting women.
- Kindhearted Cat Lover: Vincent.
- Laser-Guided Karma: Ultmately everyone gets what they deserve, for good or ill. The twins forge a permanent bond, marry a pair of good-looking, good-hearted women and each gets a set of twins of their own. Mary Ann, having long believed her only son died at birth, discovers she actually has two and gets the chance to reconnect with them. Meanwhile Webster, a Faux Affably Evil murdering bastard who killed the two men who hired him and offed Beatroot, gets violently crushed by a chain-hook and a long length of metal chains. Dr. Traven, who isn't a villain but still acted like a bitter old crank and a jackass, gets sucker-punched for his own bad deeds (because at least he didn't kill anyone).
- Loan Shark: Vincent is hounded by the family of loan sharks almost every other scene. Played for laughs, as they are continuously injured and quite non-threatening.
- Long-Lost Relative: Julius and Vincent were Separated at Birth. Vincent was placed in an orphanage in Los Angeles, Julius was taken to a South Pacific island and raised by Professor Werner. Each twin is unaware of the other's existence until Vincent learns of his twin brother in his 35th birthday.
- Mama Bear: Mary Ann, after she learns about Dr. Traven's little white lie. "You stole my family... you lying son of a BITCH!!"
- Manchild: Julius has a lot of child-like innocence due to spending his whole life on an island.
- Missing Mom: Julius was informed that his mother died in childbirth. Vincent believed his mother abandoned him.
- Mistaken Identity: When they first meet, Vincent thinks Julius is a debt collector working for the Klane brothers.
- Mix-and-Match Man: Julius and Vincent are Designer Babies with combined DNA from six athlete and scholarly fathers. Vincent lost out in the process though.
- The Morality/Mortality Equation: Beatroot's associates get killed just for seeing Webster's face, even though as far as the audience is aware they're just a couple of guys doing their job. Beatroot himself suffers the same fate near the end, for the exact same reasons.
- Nature Vs Nurture: Because of the unexpected birth of twins, the experiment was ended and the mother/children split up. Julius ended up with one of the scientists who genuinely raised the boy to be a genius bodybuilder ("the Good") in an isolated environment void of cultural distractions. Vincent was left abandoned to an orphanage, without any mentor or guidance to grow up, and learned to cheat and lie his way through life ("the Bad") while living a hedonistic unhealthy lifestyle. The argument would be how much did genetics already establish which twin was Good or Bad, and how much did they grew up the way they grew up? Lampshaded by Julius, who realizes he had the more coddled childhood and condemns Dr. Traven for pre-judging Vincent to a harsher life."I was taken to a beautiful island, protected, educated, loved, given every opportunity to grow, to dream, to create. But you had none of that. You had nobody. Nobody to love you, nobody to trust you, nobody to encourage you. All life taught you was that the only person you could count on was yourself."
- Nice Guy: Julius.
- Noble Demon: Beetroot honors the deal he made with Vincent, even though he realizes by then that Vincent obviously got ahold of it by accident, and probably doesn't even "know what the hell this thing is"; after explaining what it is, he leaves the promised payment and leaves with the goods. Unfortunately for Beetroot and his assistant, Webster isn't noble at all, gunning them down in cold blood just before Julius arrives, leading to the climax.
- Oh, Crap!: Vincent's celebration of getting his money is cut short when he hears gunshots and Beetroot's car crashed.
- Overly Long Gag: The chain.
- Pet the Dog: Or cat in this case. Vincent, despite being a moneygrubbing lech until he meets Julius, is very kind and loving towards his pet cat, ironically named Julius.
- Dr. Werner had hoped Julius would stay with him after learning he had a twin, but Julius was insistent on leaving to find his twin brother, so Werner let him leave. That's as nice as he gets and it's all downhill from there.
- Polar Opposite Twins: Duh.
- Psycho for Hire: Webster. He kills anyone he meets in person so they can't identify him, even if that person is the one who hired him.
- Raised by Dudes: Arnold's character is raised by scientists (with one of them being more of a father figure to Julius) while his biological parents (all seven of them) are excluded. When he ventures into normal society, he is very much a Fish out of Water.
- Rule #1: The rules of a crisis situation:Rule 1: Don't move too soon.
Rule 2: If you choose to bluff, you must be prepared to have your bluff called.
Rule 3: Duck.
- Separated at Birth: Natch. All because of Dr. Traven.
- Something Else Also Rises: When Marnie falls asleep on Julius, it causes his bicep to bulge to the point where it rips his shirt.
- Took a Level in Jerkass: Of course Vincent was kind of a jerkass his whole life, but became a bigger jerkass after he was told their mother died and took it out on Linda and Julius.
- He was also told that he wasn't planned and was made out of everything they didn't want in Julius. That certainly didn't do much for his mood.
- Twin Telepathy: Naturally. The Twins are even in constant synchronization, much to Vincent's initial annoyance. Vincent named his first cat Julius, and Julius named his first computer Vincent. When either brother is hurt, both feel pain. Vincent actually gives up the five-million-dollar payoff in an attempt to rescue Julius he's pretty sure won't work specifically because Julius has given him a conscience that won't quit nagging him.
- Virgin-Shaming: Julius is revealed to be a virgin, unsurprisingly since he's spent his whole life on a desert island with no women around, and is embarrassed when Vincent teases him about it.
- Whatever Happened to the Mouse?: We never find out if the loan sharks are still after Vincent. Though after getting the reward money, he likely paid them off, or they were arrested at the bar.
- Wide-Eyed Idealist: Julius.
- Wins by Doing Absolutely Nothing: Near the beginning, a motorcycle-riding thief tries to steal Julius's suitcase. Julius is so strong that he is able to hold onto the suitcase without even noticing that the man was trying to steal it, which yanks the thief right off his motorcycle. Julius actually thinks the man got caught on his suitcase and unironically tries to give him medical assistance while apologizing profusely.