It starts off with Frankie and Madame Foster leaving for the day, but before Madame Foster leaves she gives a warning not to throw any wild parties while she is gone. Bloo hears this and begins to plan the party, although Mr. Herriman demands that he doesn't. Bloo realizes he needs to remove Mr. Herriman if he wants to throw the party and he asks the other friends for opinions. Coco gets a plan and she calls Mr. Herriman and tells him that his refrigerator is running, so he runs out the door to catch it.
After Mr. Herriman leaves, the party starts and everything goes as Bloo had planned. However, The Duchess gets upset that Bloo is having a party and she tries to get him to stop. Mac arrives and he also disagrees with the party because it was against the rules but Bloo insists that nothing bad will happen. The Duchess decides to try to call Madame Foster while Mac continues to try to reason with Bloo, until Bloo asks him if he wants some candy, causing Mac to panic and run away because Mac too easily succumbs to the effects of Sugar.
While Mac is running away, Coco and another bird like Imaginary Friend are looking at someone they find attractive, which we were lead to believe Coco was interested in a rooster Imaginary Friend but when he ran to pick her up in his arms, she ignored him and ran to a lamp, in which she spent quite a lot of company with throughout the episode. Mac unfortunately runs into someone holding a bowl of super sweet punch, which due to Bloo's request had way too much sugar in it. A drop of the punch landed in Mac's mouth causing him to go into a sugar rush.
Mac looses control of himself due to the sudden intake of extra energy and begins to run around the house consuming every bit of Sugar he can get. Meanwhile Wilt and another Imaginary Friend are having a Dance Contest because the other Imaginary Friend was made for the purpose of dancing, which made him feel like he was being challenged by Wilt's dance. Mac continues to storm around the house, which causes the other Imaginary Friends to complain to Bloo about how Mac is ruining the party.
Mac eventually ends up on an above balcony which was over the main room of the party, he consumed soda and a substance similar to pop rocks at the same time and grabbed the "Bloo's House Party" banner and began to swing around the room. This caused Eduardo to literally drop and loose his marbles, which caused Wilt to start slipping on them which then caused him to appear to dance in an incredible fashion, making him the winner of the dance contest. Unfortunately, Coco's lamp was broken due to Wilt's eventual fall, and the bird lost her one true love.
Mr. Herriman returns to Fosters because he remembered that is where his refrigerator lived, after he scolded it for running he began to figure what happened while he was gone. Bloo convinces him that he will be the one responsible for the party since he allowed all this to occur while he was in charge. Meanwhile Mac runs away in the nude causing them to chase after him. They needed a vehicle fast enough to catch up to him and Bloo wanted to take the bus, but since it was already taken they got in Madame Fosters car and went after him.
Bloo was driving the car while Wilt was pressing down on the gas, and although they were speeding they did manage to find Mac. Bloo coaxed him into the car by giving him a piece of gum, but the gum was Sugar free so it prevented him from getting the energy to escape. On the way back to the home the car stopped at a stop light, but as they did so did Frankie and Madame Foster in the Fosters Bus. Frankie saw them but as she took a second glance they put on horrible disguises and managed to get away. But Eduardo, who was chasing them all this time on his tricycle, said hello to Frankie causing her to decide to get the bus back to Fosters before Bloo and the others did.
When Bloo, Mr. Herriman, Wilt and Mac get back at Fosters, they find that Frankie and Madame Foster are already there. Bloo tried to put the blame on Frankie and Madame Foster but it doesn't work, and when Madame Foster is about to punish Mr. Herriman for breaking her rules, she states that the real rule was to throw no wild parties without her, because she loved wild parties.