One magical day, June is running through the woods to find her way home where she discovers an old rollercoaster car and climbs inside. She suddenly finds herself in Wonderland, an amusement park she had created in her mind and put aside. All of her rides and characters are brought to life but are falling into disarray without her. Now, with the help of her fun and lovable park characters, June will have to put the wonder back in Wonderland before it is lost forever.

Junie B. learns some interesting things about the Tooth Fairy when she becomes the first student in Room One to lose an upper tooth.