Didn't Think This Through: Thinking her mother would go to the play if she had a nice dress, Ginny secretly sells her hair to a wig maker and buys her one. Della thinks the dress is yet another gift from Harold Mayfield and that Ginny is plotting against her, leading her to send her daughter to her bedroom without supper.
Excessive Mourning: Harold Mayfield tries to argue that Della has been mourning for her husband for too long (she'd been a widow for two years), and that he's a widower himself and the last thing his late wife would want is for him to waste his life in grief. This comment only offends Della, and Mayfield realizes he screwed things over.
Foreshadowing: Mrs. Oleson presents a wig maker responsible for making Nellie's wig for the play, during which he explains how he has to pay a good amount for the hair needed to make wigs. It's a sign of how Ginny gets the money to buy her mother a new dress.
It's All About Me: When it's revealed that a tearful Ginny cut off her hair for real so she could sell it to a wig maker to buy a dress and get her busy mother to come and watch the play, all Nellie Oleson cares is about when she can say her next line and be in the spotlight.
Karmic Butt-Monkey: Willie doesn't get the best luck throughout the episode, but it's all self-inflicted: he impersonates Robin Hood with his mother's hat to torment the Ingalls girls, and is beaten by Laura and implied to get a spanking offscreen from Mrs. Oleson for getting her favorite hat; then he tries to repeat the act with a stray dog during recess and gets chased into the school. Finally, he convinces two older classmates to do his play under the condition that he'll get cigars and chewing tobacco from his father's store, but he fails to get them and gets into an argument with them, which gets him covered in the white paint they'd use for the play (it was Tom Sawyer), and gets laughed at by everyone present.
Maybe Ever After: After being rejected by Della Clark throughout the episode, Harold Mayfield is seen giving her and Ginny a ride home after they make amends during the school play, implying that she might give him a chance after he helped her with her daughter.
Papa Wolf: While he isn't Ginny's father and his fondness for her is partially because he's interested in her mother, Mayfield gets furious when Della refuses to go see her daughter's play and confronts her in Ginny's defense after seeing the girl in tears for not being able to convince her mother with the new dress (Della thought it was a gift from Mayfield to try and court her and rejected Ginny's request to wear it to go watch her play, unbeknownst that Ginny had sold her hair to buy it).
School Play: After an incident where Willie tries to play Robin Hood to torment the Ingalls girls, Miss Beadle suggests that the kids use that creativity of theirs to do something more constructive, which leads to the idea of the kids making stage plays in the story.
Selling One's Own Hair: Ginny uncovers her head and reveals that she sold most of her hair to buy her mother a dress so she could come and watch the play — it's what helps her and her strict mother make amends.
Shipper on Deck: Ginny wishes that Mr. Mayfield and her mother became a couple, but she's not initially interested in him.
Struggling Single Mother: Widowed Della Clark is often busy due to having to provide for herself and her daughter Ginny and that's why she's initially uninterested in the school play (or in Harold Mayfield's courtship).
Sword and Fist: Laura challenges Willie for a sword fight when he keeps tormenting her with his wooden sword (she uses a stick), and when he gets to disarm her, she jumps on him and it becomes a regular fight.
