The Country Cousin tells the story of a mouse from "Podunk" (an American English name denoting a place "in the middle of nowhere") coming to visit his relative in the city. The opening shot/title card is of the mouse in question, Abner, staring up at the city skyscrapers, with the sign directing him to Podunk facing the opposite way. He receives a telegram (titled a "Mouse-O-Gram") from his cousin, Monty, telling him to "Stop being a hick" and come live with him in the city. Without specifying the location of Abner or Monty, the film sets out to contrast the lifestyles of the archetypal country and city inhabitants.
Abner is shown walking along a railroad towards the city, and when he arrives, the differences between the two become clear. Abner is wearing overalls and is portrayed as bumbling and oblivious to the dangers of the city, whilst Monty sports a top-hat and is acutely aware of the problems they face (as exemplified whenever he tells Abner to shush, which is also the only sign of dialogue here). Monty leads Abner to a meal that the human residents of the household have set out. The two mice begin by dining on cheese, but Abner lacks any sense of etiquette, and soon begins gorging himself on celery, cream, and mustard, the latter of which generates a reaction to the excessive heat. Cooling himself with Champagne, Abner finds himself partial to the taste, and becomes inebriated, provoking the disdain of Monty. Abner begins seeing in double vision, and creates more noise by bringing down a pile of bread.
Abner then assesses his reflection in a block of jelly. As he walks away, he slips on a piece of butter lying on a saucer. The saucer, spinning and flying across the table, catches Monty on the way, and breaks several pieces of dishware too. Monty is infuriated, and as the pair are now on the floor, he attempts to find a secluded spot, safe from the sleeping pet cat. Abner, with a great sense of bravado, kicks the cat's behind, whilst his cousin rushes back to his home (and is never seen again from that point onwards). The cat bares its teeth at Abner, which only leads him to inspect the inside of its mouth, thus bringing Abner back to his senses. He is then chased by the cat, first receiving an electric shock by jumping inside a socket (the cat receives a shock as well), and then ending up on the city street when he jumps out of the window.
Abner is faced with escaping from the footsteps of the people, a bike, an electric tram, and other vehicles. He finds himself at the city limits again, and flees back to his home town.
- In the book Disney Dossiers: Files of Characters From the Walt Disney Studios, this short is listed as one of Mickey Mouse's filmography highlights, despite that he does not actually appear in it.
- The footage of Abner Countrymouse dodging traffic was reused in the 1947 short Mickey's Delayed Date, while the footage of the blaring horns was reused in the 1953 Goofy cartoon How to Sleep.