The Wearing of the Grin is a Looney Tunes (reissued as Blue Ribbon Merrie Melodies in 1960) cartoon directed by Chuck Jones and written by Michael Maltese. It was released theatrically on July 14, 1951.
It was the final cartoon featuring Porky Pig as the only major recurring character. Porky had been Warner Bros. animation’s first major star until had been supplanted first by Daffy Duck (a phenomenon that was even satirized in toon form in Friz Freleng’s You Ought to Be in Pictures), and later by Bugs Bunny. As this had progressed, Porky starred in fewer solo cartoons. All of Porky's subsequent appearances in the classic era would be with other characters such as Daffy or the non-speaking, house cat version of Sylvester.
The title refers to The Wearing of the Green, an old Irish ballad, while the green shoes themselves are borrowed from the Hans Christian Andersen fable The Red Shoes (and the 1948 film based on it) about a pair of ballet shoes that never let their wearer stop dancing. The title was parodied, also as "The Wearing of the Grin", in the Bugs Bunny cartoon What's Up, Doc?, where Bugs reveals that being in the play's chorus was his first gig as an "actor."
While traveling through rural Ireland on his way to Dublin, Porky Pig is caught in a storm and asks for lodgings at a nearby castle, but the caretaker, O'Toole, tells him that no one inhabits the place but himself and the leprechauns. Porky dismisses the remark, but then a mace accidentally falls and strikes him on the head, knocking him unconscious. At that point, "O'Toole" is revealed to be a pair of leprechauns disguised as a human being. O'Pat, the first one, is very calm while O'Mike, the second one, is frantic that Porky is after their pot of gold. O'Pat, being the "Chief Leprechaun", convinces his partner that he knows how to deal with the pig.
When Porky wakes up, he is helped to a room by a "reunited" O'Toole who, during the short trip to the room, gets accidentally divided in two again. As Porky notices, he mentions to the top half of O'Toole that he has lost his lower half, and seeing that "O'Toole" is actually two leprechauns, is terrified and runs and hides in his bed, which happens to be a trap door leading to a shaft where Porky drops until he falls into the witness chair in a courtroom. There the leprechauns charge him of trying to steal the pot of gold and sentence him to the wearing of the Green Shoes.
At first Porky appreciates them as some nice shoes, but soon he realizes that they are cursed, as his feet begin a frantic Irish jig. The shoes will not stop dancing, and even when he removes them, they chase him and return themselves to his feet, and he is "danced" through a nightmarish landscape filled with Irish icons until he falls in a boiling pot of gold. At this point, he wakes up to find himself in a puddle of water still standing where he fell after being hit by the mace. Panicked and disoriented, he runs away from the castle. O'Toole watches him run, shaking hands with himself (actually O'Mike, the other leprechaun) with a mischievous smile, over a shamrock-shaped iris out."The Wearing of the Grin" is the name of one of the Broadway shows featuring Bugs Bunny as one of the "Boys in the Chorus" in What's Up Doc?
The Leprechauns from the cartoon can later be spotted during the basketball game in the bleachers in Space Jam.
The Leprechauns make their return in the SNES game of Porky Pig's Haunted Holiday
The Wearing of the Grin is available on the Looney Tunes Golden Collection: Volume 1 DVD box-set, supplemented with an audio commentary by animation historian Michael Barrier.