This means that he can go "BOO!" really loudly. His pet ghost named Squiggle has Squiggle Power, which means that he can fly and do really fast loop-the-loops. Together they have the world's greatest ghost adventures! They enthusiastically frolic and roughhouse, having ghost races and drinking melted ice cream, but they often accidentally hurt each other's feelings, and have to comfort and console one another. In Book 1, when the giant pink and yellow Ice Cream Monster bumbles into their lives, they go into a mad panic... until they discover that he's actually quite friendly.
Kid tested in the home of James Kochalka, Johnny Boo is hilarious and certified gold.