Smarty is one of Rollan's orphan friends.
Smarty is most likely dimwitted or a smart aleck, as it is stated by Rollan that is name is a joke, not a compliment. He and Rollan were trying to get some willow extract for Digger. Instead of waiting to see if Rollan would get the medicine, he rushed in and stole the willow extract which got Rollan in trouble. He probably gave Digger the willow extract but it is not yet confirmed.