Tromeo and Juliet

Tromeo and Juliet kill Cappy, but are informed by Ingrid that they are actually siblings. They decide they don't care and six years later, have a family of (deformed) children and succeed in bringing the warring families together.

Long Ending:
The film is narrated by Lemmy of  Motörhead and even incorporates actual dialogue from Shakespeare's play.

In NYC, there are two warring families, one led by the drunk, poor and sickly Monty Que, whose son is Tromeo (Will Keenan). The other is lead by the wealthy but sadistic Cappy Capulet, whose daughter is Juliet (Jane Jensen). Tromeo is obsessed with finding love, although all the women he hooks up with end up cheating on him. Juliet, meanwhile, is kept locked in her house where her dad beats both her and her mother, Ingrid. The Capulet's maid, Ness, has fallen in love with Juliet and, though the two are romantically involved, Juliet dreams she will find someone she truly loves.

Tensions flare when  the families fight at a club and one of the Capulet's fingers are cut off with a paper cutter. The NYC cops have had their fill of the feud and keep a closer watch on the families. It is revealed that Que and Cappy had formed a lucrative film company a number of years ago. Que's was married to  Ingrid at the  time. Ingrid eventually has an affair with Cappy and divorces Que, takes his half of the company in the divorce, marries Cappy, and gives birth to Juliet. Since then, Cappy's insanity has almost driven the company under and so he has arranged for Juliet to marry a billionaire meat processor named London Arbuckle.

Tromeo and his cousins sneak into a Capulet Halloween party where Tromeo sees Juliet with Arbuckle. He immediately falls in love and after he gets Juliet alone, she falls for him as well. Later that night, a drunken Cappy chains Juliet  inside a glass cage before passing out. Tromeo sneaks into the house with the help of Ness, sneaks into the cage, and has sex with Juliet. The next morning, they agree to get run off and get married. Juliet breaks things off with Arbuckle, they are married by Father Lawrence, and have tons of passionate sex.

When the Capulets find out, they hunt down Tromeo and his cousins and a fight breaks out, with several people on both sides dying (one is stabbed through the eye with a tattoo gun, another's head is bashed in, a third has his arm ripped off and is decapitated). Meanwhile, Cappy beats Juliet until she agrees to take Arbuckle back and marry him the next night. Father Lawrence (who is helping the young lovers since he, too, once found love, with a pre-teen boy of course) puts Juliet in touch with the local drug dealer Fu Chang who gives her a drug that will turn her into a beast until her true love finds her. Father Lawrence then goes off to find Tromeo and bring him to stop the wedding.

Juliet takes the drug and is turned into a giant cow monster with a huge penis. Arbuckle is absolutely repulsed and jumps out a window rather than marry her. In a fit of rage, Cappy tries to kill Juliet, but Tromeo (with the help of Father Lawrence and Ness) arrives just in time to stop him. Cappy has a huge fight with the two lovers (wherein he is burned with a curling iron, stabbed with a nail file and tampons and has a TV smashed on his head), but Cappy eventually gains the upper hand. Juliet eventually electrocutes him, to end the madness. The police arrive and agree that all the deaths were caused in self-defense, praise the foursome for helping to clean up crime and even offer Father Lawrence a job.

Tromeo and Juliet prepare to drive off when Que and Ingrid stop them. Ingrid reveals that Tromeo is actually her and Cappy's son (conceived when they had an affair). She initially told Que that Tromeo was his son and, after revealing the truth to Que,  let him raise Tromeo in return for Que signing away the film studio rights in the divorce. So, in actuality, Tromeo and Juliet are siblings. The lovers look at each other for awhile and ultimately decide they don't care and drive off into the sunset anyways.

Six years later, we see Ingrid, Que and several of the cousins at a BBQ at Tromeo and Juliet's house. The pair have two deformed but happy daughters, but have also just given birth to a normal-looking baby boy. The families have officially united. 

Thanks Evan B!