It's Pluto's birthday and Mickey Mouse is busy preparing the party things for his birthday dog, Pluto. First, Pluto tries to eat the cake, but is caught by his master, Mickey Mouse, when it is time for his bath. As soon as Pluto is looking more neat and tidy, he tries to eat the cake but then gets spotted by his master again. Then, Mickey's nephews/sisters barge the gate down and trample all over Pluto as they hurry to the party. The children give Pluto a small red cart and treat him like a workhorse. They then all start to enjoy themselves at the party. They first take Pluto on the slide, then barge down the swing. Then, they play pin the tail on Pluto to see who can pin Pluto's tail. Soon it is time for lunch and Pluto wants to have a piece of his own cake, but Mickey's nephews/sisters prefer to amuse themselves by grabbing every slice of cake and eating it up, much to Pluto's horror. Eventually, they devour Pluto's birthday cake and leave. Pluto, understandably upset, angrily throws a tantrum, knocking away all the dishes until Mickey passes him the last slice of the birthday cake he saved. Pluto happily eats the cake, licking Mickey between bites to show his gratitude.