Chugger was an infant male squirrel orphan. He was kidnapped by a group of Flitchaye and would have likely been eaten had it not been for the efforts of Martin the Warrior, Dinny, Gonff the Mousethief, and Trimp the Rover, who rescued him. Previously, he lived in the forest with his grandmother, but one day, she passed in her sleep. Chugger shook her but she didn't wake up, leaving him on his own until his kidnapping and rescue by the four travelers.
Trimp looked after Chugger as if he were her child. The young squirrel was later kidnapped by carrion crows, but he escaped with the help of Krar Woodwatcher.
Chugger helped Folgrim with his mental trauma and they eventually became very fond of each other. He had no fear of Folgrim, despite the warrior otter's frightening appearance. When Martin and his friends brought Vurg, Denno, Dulam, and Beau back to Redwall Abbey, Chugger adopted them as his four grandpas. While there, Chugger quickly befriended Baby Gonflet, who taught the squirrel the art of pie stealing. He and Trimp were brought into Gonff and Columbine's family.