Here, as in Frederick's Alligator (1980), Peterson's single notion gets a lot of help from Natti's perky, beckoning illustrations. The only wheels that Penelope can afford--after getting the grand sum of $11.50 for her birthday--are roller skates; but on the day everybody heads for the ballpark ""to see Slugger Jones hit his hundredth home run"" (the only post-skates happening), she beats both motoring neighbor Mr. Smith and bicycling friend Jim to a seat: Mr. Smith got caught in traffic, Jim had to look for a place to lock his bike. It's pretty thin and a little lame--but a youngster can recognize the transport situation and identify with Penelope's triumph. What keeps the pages turning, though, is the spontaneity of the drawing and the expressions on the faces.