Closed Door Rapport

Please, I know you're in there
People are asking where you've been
They say, "have courage" and I'm trying to
I'm right out here for you
Just let me in
We only have each other
It's just you and me
What are we gonna do?

—Anna, Frozen

In fiction one great way to up either the drama or comedy of a conversation is to have it occur through a door. One party shuts the other out in attempt to avoid the confrontation while the other desperately tries to communicate in spite of the obstructive barrier.

This setup is useful in providing physical distance between characters to mirror psychological separation, and for its flexibility in resolution. This distance may just as easily be broken down by the opening of the door as suspended indefinitely by the character choosing not to emerge. Usually the character behind the door is the more emotionally closeted of the pair while the character on the outside is more honest and straightforward, having to persuade the other that opening the door is not a bad thing.

Most commonly portrayed with romantic relationships and between parents and children who don't see eye-to-eye. Occasionally accompanied by the stock phrase "let me in" because "let me into the room" is an easy metaphor for "let me into your heart."

Sister Trope to Separated by the Wall. Locked in the Bathroom can show up as a comedic variant.

Examples of Closed Door Rapport include:

Anime and Manga

In The Weatherman Is My Lover Koganei goes to Amasawa's apartment when he skips out from work and they have a heart-to-heart on opposite sides of door, culminating with Koganei's request, "Won't you let me in? Let me into your heart, Amasawa." Amasawa decides to take his chance.
In Junjou Romantica when Nowaki confronts Hiroki about their breakup at Hiroki's workplace, Hiroki runs back to his office and locks Nowaki out causing a bit of a scene. He is not persuaded to open the door.
In Tsubasa Reservoir Chronicle, this happens when Sakura hides into her room leaving Shaoran outside in the chess world.
Ef a Tale of Memories has Hiro and Kei separated by a door as they work out her unlucky childhood friend status.
Episode 5 of Suite Precure used this for one of the show's most emotional scenes (so far).
Nori and Jun played this trope straight in Rozen Maiden.

Film

In Love Actually Liam Neeson's character often talks to his step-son through the door, as Sam hardly leaves his room after the death of his mother. Sam mainly responds by leaving notes on the door itself.
Hitch does this toward the end of the movie.
The Negotiator milks this for all it's worth—both Danny Roman and Chris Sabian are introduced doing this. Roman is talking with a gunman. Sabian is talking with his wife.
In Half Baked, Thurgood and Mary Jane have a conversation in this fashion.
Across the Universe had this for one of their musical numbers. Prudence, who had a crush on Sadie, ends up locking herself in a closet after she realizes that Sadie and Jojo are now a couple. So the gang (minus Sadie and Jojo, incidentally, who have a thing they have to get to) sing "Dear Prudence" to try and convince her to come out of the closet, get out of her funk, and see the world for how wonderful it is.
In Beauty and the Beast, Belle and the Beast have an angry discussion through her door when she refuses to come to dinner.
In the first and third Back to The Future movies, Doc runs into another room in disbelief of Marty's statements that he's from the future.
The Aviator between Howard Hughes and Katharine Hepburn. Hughes has locked himself in his room because of his fear of disease, and former Love Interest Hepburn turns up to rally his spirits.
Disney's Frozen has a song, "Do You Want To Build A Snowman?", that fits this. It is barely a duet.

Fan Works

"Do You Want To Build A Snowman?" parodies, like this and this.

Literature

Invoked by Jesus in the Book of Revelation: "Here I am! I stand at the door and knock. If anyone hears my voice and opens the door, I will come in and eat with him, and he with me." (Rev 3:20, NIV).
Fire invokes this trope when Nash comes a-comin'.
After Betsy the Vampire Queen, possessed by the Book of the Dead, attacks Jessica and nearly kills her, Jessica locks herself in her room. Betsy (full of remorse) leaves her a baby monitor and communicates with her via it for most of the book (although Jessica doesn't respond).

Live-Action TV

In the third season of Skins Naomi and Emily have one of these, in what is probably the most emotionally resonant moment of the whole season.
In the episode "Dinner at Eight-ish" on Cheers, Lilith, Frasier, and Diane each retreat into the bathroom after different arguments over their relationships. Discussions continue through the door for the rest of the episode.

Music

The J-pop song "Laugh Maker" by Bump of Chicken is about the titular character trying to convince someone who's been crying alone to let him in so he can cheer them up. The person eventually gives in, but discovers that the door is stuck and Laugh Maker has seemingly abandoned them. Just as they start to give in to despair, Laugh Maker breaks in through the window.
- The Touhou-based spinoff "Locked Girl" features Mar isa repeatedly urging Pat cho uli to open the library door and come with her. Patchy's a bit too reluctant to try, so Marisa eventually resorts to using the Master Spark to blow the door to pieces so she can finally get through.

Theatre

Played for Laughs in The Comedy of Errors, where the door is used to obscure the identity of Separated at Birth twins from one another as they argue.

Web Comics

In The Meek, Phe locks her husband Luca out of their bedroom after a heated argument got out of hand and gives him an ultimatum; he can have his revenge, or her, but not both. It's not until Luca apologises does Phe open the door and drag him inside for make-up sex.

Western Animation

In Lyle, Lyle, Crocodile, the HBO Storybook Musical version of The House on East 88th Street, Lyle locks himself in the closet when his old owner arrives to take him away from his new family, and Joshua sings to him through the door.
In South Park Tom Cruise locks himself in Stan's closet, over the corse of the episode multiple people try to talk him into coming out.