The Wearing of the Grin is a 1951 Warner Brothers short released under the Looney Tunes banner. It was released as a Blue Ribbon Merrie Melodie as well. It was originally released July 14th, 1951, and was re-issued sometime in the '59-'64 season. The production code is unknown due to the fact that none shows up on screen.
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 hits his head and he loses consciousness. 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.
The Leprechauns from the cartoon later can be spotted at the bleachers during the basketball playoff against the Monstars and the Tune Squad in Space Jam, and also had a cameo in the Histeria! episode "The Dawn of Time".
This is Porky Pig's final solo cartoon. Porky, who had starred in many solo cartoons in the 1930s till the early-1940s, starred in lesser solo cartoons since the mid-1940s due to Daffy Duck (and later Bugs Bunny) surpassing his popularity. After this cartoon, all of Porky's subsequent cartoons are paired with other characters.