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Tear Jerker: The Twilight Zone
In "The Lonely", a prisoner condemned to live alone on an asteroid is given a female robot for companionship and falls in love with her. When he gets a pardon, there's no room for the robot on the ship home. When he refuses to leave her behind, the ship's captain shoots her. The prisoner comes to his senses and leaves the asteroid. What really clinches it is the closing narration. This robot, which he loved and which saved his life, is now obsolete and abandoned, turning to rust.
The ending part of "I Sing the Body Electric". The children, all grown up, have to move on to their new lives and new homes, yet they will still visit their electrical "grandmother" from time to time. It's so heartbreaking, and at the same time heartwarming.
In "Piano In The House", Fitzgerald Fortune plays a joke on one of the people at his wife's birthday party, a heavyset woman named Marge. He used the player piano to make Marge reveal to everyone that she secretly wishes she was as light and delicate as a snowflake, and likes to imagine herself as a graceful ballerina named Tina. While in her trance she's quite graceful. At first, everyone is laughing, until Marge reveals her secret desires and dreams of being loved by somebody, as she takes his hand into her's and melts away. Once the music is off, Marge comes back to reality and realizes what she's just done. Of course, at that point, the only person who was still laughing was Fitzgerald.
Which is followed by Fitzgerald deciding to play a piece intended to "bring out the devil", only for his wife Esther to switch the music with Brahms's "Lullaby". The music causes Fitzgerald to reveal himself for what he really is: a spoiled, lonely, and scared little boy afraid of everything, afraid of love and friendship because he doesn't know how to respond to them. He's hurt Esther because he didn't know how to respond to her love, hurt Marge because he's jealous of how she can be the life of the party with her liveliness, and criticized Gregory Walker's plays because he himself lacks the creativeness Gregory has. The partygoers, including Esther and Gregory, leave Fitzgerald upon realizing "the devil" is really a scared child, and Fitzgerald throws a temper tantrum whereby he destroys the room and the music. He begs his elderly butler, Marvin, not to laugh at him.
Marvin: I won't laugh at you, Mr. Fortune. You're not funny anymore.
"The Once and Future King" (1980's episode): An Elvis Impersonator gets sent back in time and accidentally kills the real Elvis Presley. He is forced to take his place to prevent history from changing. The ending shows the man, now in 1977, telling his manager (who had once been his girlfriend before his trip through time, and was historically Elvis' last manager before he died) his story, saying that the guilt of killing Elvis and the stress of his performances is killing him. She doesn't believe him and thinks he's just working too hard, kissing him good night. He sadly looks out the window and at a bottle of pills, most likely contemplating suicide by overdose, while "Are You Lonesome Tonight?" plays.
"Little Boy Lost" (1980's episode): A woman is trying to decide if she should marry her boyfriend now or go abroad for several years for her job. She meets a little boy and plays with him, but eventually decides to go abroad, angering her boyfriend. The boy is disappointed. He then explains that he is the son she would have had if she had stayed with her boyfriend. In tears, she says that she will marry her boyfriend, but he says it is too late, even if she has children, they won't be him. He then fades away.
In "Night Call" from the original series, an elderly crippled woman is kept getting called by someone who wants to talk to her. She screams at him to stop bothering her. Later, she got a call from the operator telling her there was no other line calling her, and tells her a telephone wire fell on a graveyard (during the storm most likely). She went there and sees a wire fell on her fiance. She recalls to her nurse that she was very demanding at having things her way; one day she took the wheel and lost control, she crashed and he flew through the windshield, and left her crippled. She realized he's calling her so she won't be lonely. She was waiting that night and he finally calls. But he called to tell her he'll leave her alone, because he always does what he tells her. She begs him to talk to her and she didn't mean what she said. Hearing no answer she cries, realizing she's alone again.
It's a blink and you'll miss it type of moment, but Jason Foster gets one in "The Masks". At about ten to midnight all his family has to say is about how unbearable their masks are. He asks "is there nothing else you have to say to me?" in a tone of disappointment and he just gets more complaining while being called crazy. From his tone of voice, it sounded as if Jason still had at least one small hope that his family could show some kindness, but instead all they give him is incessant pettiness and cruelty.
Also, during his "The Reason You Suck" Speech, he mentions that Emily's marriage to Wilfred "broke the heart of her dear, late mother, in just about every sense of the word." For some reason, this has been omitted from most broadcasts, but just goes to show that Emily's self-absorbed spinelessness affected more than one person for the worse.
"The "Big Tall Wish." A washed up boxer is able to win his comeback match thanks to the wish his girlfriend's son made. The boxer discovers this and feels that something like a wish is an impossible explanation, and despite the boy's heartbreaking pleas to believe in it he just can't, and ultimately the wish is undone.