They are stray dogs who hang around a junkyard. They are also common enemies of Riley's Gang. Ashcan is a Boxer and Pete is a Bullmastiff. Ashcan is the more intelligent one, while Pete is the idiotic sidekick. Apparently, Ashcan once killed a dog just for stepping on his tail. Going by Ashcan's comment upon meeting Sassy, they eat cats.
They are first encountered in the film when Shadow, Chance and Sassy stumble onto their territory. Although Shadow tells them that they mean no harm, Ashcan fights with Shadow, while Pete tries to eat Sassy (who heads for high ground and drops a flowerpot onto Pete's head). Riley and his gang show up, however, and drive them away. Chance fled upon noticing Riley's Gang, due to mistaking them for reinforcements.
Later, Ashcan and Pete are lazing off at the junkyard, and Ashcan mentions to Pete that he thinks he hears something (although it's implied that he was trying to trick Pete in order to keep him away from his chew toy). However, Pete, thinking that Ashcan really did hear something, informs him that he was right and says he sees Shadow and Sassy passing the junkyard. Ashcan prepares to ambush them but fails due to Pete misunderstanding Ashcan's usage of the word "you," in terms of who was going to ambush them.
They reappear later in the film and confront Shadow and Sassy again at a construction site. Shadow and Ashcan fight, while Pete corners Sassy (although she does, nonetheless, manage to land a scratch from her paw at Pete just prior to the fight), but she and Shadow are saved by Chance's entrance. Chance leads Ashcan and Pete on an "obstacle course" and into a section of pipe, then pushes it down a slope with them still inside. In the aftermath, Ashcan and Pete blame each other for who got them trapped in the pipe before Ashcan tells Pete to "shut up." Ashcan and Pete presumably give up after this, as they're not seen again.
- Apparently, Pete was once a pet as evidenced by his collar. He was either abandoned by his owners or just left them at one point.