The eponymous heroes of this early reader are two genial, googly-eyed earthworms who are also best friends. In five short chapters, Wiggle and Waggle (the latter, distinguished by a pair of glasses) learn that singing makes a job go faster; a difficult task—moving a big rock out of a tunnel—is made easier when individuals work together; and a rainy day needn’t be a spoiler if you have an upbeat outlook. Arnold’s (Super Swimmers) writing has an easygoing cadence and just the right amount of repetition (“They dug long tunnels, short tunnels, fat tunnels, and thin tunnels”), although her wrap-ups for each story can be fairly anticlimactic (after a day of singing and digging tunnels, Waggle muses, “We are a good team…. Let’s dig again tomorrow”). Peterson (No Time to Nap!) is all-around terrific, tightly cropping her environments to keep the action focused on her characters and conveying a sense of contrasting scale (an unharvested carrot dwarfs the two worms). As for the two leads themselves, they’re spunky, comically gangly and just vulnerable enough to be adorable. For youngsters smitten by this duo, a list of facts about worms and how they contribute to a healthy garden concludes this cheery collection.