Barko is a Scottish Terrier, who belonged to Pops back when Pops was still a travelling salesman for the Elfwood Candy Company. Barko pulled Pops wagon with candy.
When Pops first met Queen Grogda, she completely ignored him, but gave Barko a bone from the wild boar she had just killed. After Grogda and Pops eloped together and went to live in a treehouse, Barko also lived with them there. Barko was however left behind in the woods when the treehouse was burned down by Gnomes. In the present, when Bean, Jerry and Luci come to pick up Elfo with The Compensator, they see a whole pack of Scottish Terriers, implying that Barko found himself a mate and had a family after he was abandoned.