Stacy is an excitable badger seen in Badger Pride. She is either friends or sisters with Becky (it is never implied which).
In the episode Badger Pride, she and Becky befriend Marlene and Private. Private is initially fearful of the badgers, but Stacy helps win his heart by giving him a Peanut butter winkie.
After a fun day, Stacy and Becky start badgering Marlene to do wild and crazy things with them. Eventually, Marlene gets so annoyed she tells them to stop badgering her. Unfortunately, badgers do not take kindly to badger stereotyping, so Becky and Stacy start chasing her around, telling her that when they're finished, her own mother wouldn't recognize her (although, as Kowalski points out, her right foot is very distinctive; even her mother would recognize that).
Stacy and Becky are later defeated when they and Marlene fall into the park, causing Marlene to turn into her feral self.
Stacy is notably used as a boomerang by Feral Marlene to knock out Becky.