Cosmo and Wanda have caught the fairy flu and whenever they sneeze, their magic effects everything around them. This is problem trouble for Timmy, who has been invited to a birthday party for Tootie, Vicky's little sister. Unlike her older sister, Tootie is madly in love with Timmy!
Timmy is frustrated because he got invited to Tootie's birthday party. To which he also mentions that Tootie has a huge crush on him. Yet worst of all, she is also Vicky's little sister. Meanwhile, Cosmo started to sneeze a lot, and it turns out that he's got the "fairy flu" which results in losing control of his magic; every time he sneezes, something random would happen. For example, he accidentally wished Timmy's house to the moon. Afterwards, Timmy arrives at Tootie's birthday party. When Timmy gets to the door, Cosmo sneezes and changed Timmy's head into a toilet seat. When Tootie answers the door, hoping it was Timmy, she screams and calls Vicky. After Wanda turns Timmy's head turns back to normal, Vicky scolds Timmy for trying to scare her sister. Tootie then returned and was happy to see that Timmy came to her party.
Inside the house, Vicky tells all the kids, who she calls "little skid marks" that she is the "absolute ruler" of the party because she is older than them. Cosmo then sneezes again and turns her into a frog, which all the kids cheer for because they thought it was part of the magic show. Later during a game of spin the bottle, more chaos ensues when Wanda also catches the Fairy Flu and turns Tootie's lips into a bear trap when she tries to kiss Timmy. As Tootie chases Timmy around her house. Her head is changed into a variety of dangerous objects including scissors, a chainsaw, and even a Swiss army knife. Later it was revealed by the two sick fairies that the cure for the fairy flu is sauerkraut, but to make matters worse, Vicky was turned into a dragon because of Cosmo's sneezing and she starts terrorizing and tearing up the party.
Timmy tells Tootie to help him stuff his fairy godparents in the form of balloons, to which he tells her are "Rare German Balloons". After stuffing them with sauerkraut and dodging the rampaging Vicky/dragon, Cosmo and Wanda are cured and turned everything is back to normal, although the party and Vicky's living room was completely destroyed. After then, it was discovered that Timmy is allergic to sauerkraut after Tootie kisses him. So Vicky has to watch him while his parents went out and she brings Tootie with her, who says she will be by Timmy every second, much to Timmy's dismay.