All three of my commenters were correct, and I completely agree with Amanda -- this can be really hard, especially if you aren't one of those "remembers all the lines" people! I should mention that, although he didn't leave a comment, Comrade Landlord got almost all of these!
1)Oh, no, no, no, no, no. I can't stand it! It's too easy! The child is in love with a human. And not just any human. A prince! --- This was indeed The Little Mermaid (Disney), spoken by Ursula
2)I know it was you Fredo. You broke my heart. You broke my heart! -- Godfather II
4)End, begin, all the same. Big change. Sometimes good. Sometimes bad. --- The Dark Crystal, Augra says this to Jen
5)If you say anything, about politics, or the campaign, or what speech you have to give, or anything, I swear to God I'm gonna stab you with this fork. -- This one was hard because it is brand new, but everyone should see it!! Milk
6)I know. She's heading an expedition to China shortly. I'm to go as her servant. But only on the understanding that I am to be very badly treated. -- Sense and Sensibility, spoken by Mr. Farrows regarding Miss Margaret.
7)You know, there's nothing I like better than to meet a high-class mama that can snap 'em back at ya. 'Cause the colder they are, the hotter they get. That's what I always say. Yes, sir, when a cold mama gets hot, boy, how she sizzles. Ha, ha, ha, ha. --- It Happened One Night
8)You've made a mistake. He's a good kid. I understand. You're hot, you're super f***ing pissed. We're all real emotional. But you're barking up the wrong tree. I know this man. He wouldn't do that. --- Reservoir Dogs
9)Now, get this, you double-crossing chimpanzee: There ain't going to be any interview and there ain't going to be any story. And that certified check of yours is leaving with me in twenty minutes. I wouldn't cover the burning of Rome for you if they were just lighting it up. --- This one stumped the Comrade, but not old Hankie Pants! It was indeed from a remake of The front page - His Girl Friday.
10)...in marrying your nephew, I should not consider my self as quitting that sphere. He is a gentleman, I am a gentleman's daughter. So far we are equal. --- Pride and Prjudice, the BBC version, spoken by Elizabeth Bennett
11)Don't put it in your pocket, sir. Don't put it in your pocket. It's your lucky quarter. -- No Country for Old Men
12)No, no, no. A vigilante is just a man lost in the scramble for his own gratification. He can be destroyed, or locked up. But if you make yourself more than just a man, if you devote yourself to an ideal, and if they can't stop you, then you become something else entirely. --- Batman Begins
13)No! No! I want an Official Red Ryder Carbine-Action Two-Hundred-Shot Range Model Air Rifle! -- A Christmas Story
14)On the evening of October 7, 1989 several hundred people got together for some evening exercise and marched for the right to go for walks without the Berlin Wall getting in their way. --- Goodbye Lenin (this film is both more and less political then you might think, so if you didn't see it for either of those reasons, stop wasting time, it's amazing)
15)I will step outside the church if that's what needs to be done, till the door should shut behind me! --- Another new one - Doubt with Meryl Streep
16)Miss Haynes, if you're ever under a falling building and someone offers to pick you up and carry you to safety, don't think, don't pause, don't hesitate for a moment, just spit in his eye. --- White Christmas
17)The Wong boys were taunting me about my parents' divorce. You beat the crap out of them. You were wearing a Kristy McNichol t-shirt, tan cords and a pageboy. You spilled your mom's groceries. We scooped them into a bag. --- Saving Face, a romantic comedy about a Chinese-American Lesbian, her middle aged widowed pregnant mother and their love interests!
18)I am honored and grateful that you have invited me to your home on the wedding day of your daughter. And may their first child be a masculine child. --- The Godfather (I)
19)When you decide to be something, you can be it. That's what they don't tell you in the church. When I was your age they would say we can become cops, or criminals. Today, what I'm saying to you is this: when you're facing a loaded gun, what's the difference? --- The Departed
(This last one may be the toughest, so I'll give you a hint...it's from my favorite film of all time!)