On a day of fun and pranks in Treetopolis, the Mushas use a crafty trick to cause trouble for the Treelings, making it look like Tom and Twigs are to blame. They have to find out how to thwart the Mushas' masterful mischief to clear their names and save the big party at the end of the fun festival. It's only with Big World Magic help that Tom can really save the day.