Candy-store yuks and looks at a book-store price--and a steep drop from Wegen's inventive Balloon Trip and $ky Dragon. Billy awakens on April Fool's Day wondering who he can fool, then gets repeatedly (and stupidly) fooled himself. ""Even the teacher""--fat, idiotic, florid print dress, harlequin glasses--""turned me into an April Fool."" So, with the thought ""they're making a monkey out of me,"" he gets a gorilla suit, tertorizes all-and-sundry King-Kong-like (there was a poster in Ms room on the first page), and then can't get out of the costume. . . whereupon he lands in a baby carriage and a mad, ""mystery-gorilla"" chase ensues. Finally, back to himself, he's asked about the gorilla--and fools 'em with his answer. Wegen seems to have aimed for lowest-common-denominator pictures and text, and made it: there's even a caricature of a fat black-mama type.