The Rusties are older, outmoded robots whom Bigweld Industries no longer makes parts for. As the name suggests, they are rusty and, in some cases, prone to breaking down and falling apart (one good example of this is Fender). After Rodney moves to Robot City, he sympathizes with the Rusties and helps to repair them when they break down. As a result of this, all of the Rusties whom Rodney helped (led by Piper) appear in the climax of the movie to help him defeat Ratchet and Madame Gasket.
- Fender: Rodney's best friend who takes him in to live with him at Aunt Fanny's boarding house. His body parts often fall apart, mainly his head. He is also Piper's elder brother.
- Piper: Fender's younger sister who also lives at Aunt Fanny's boarding house. She finds Fender annoying but cares for him very much, standing up for him to Jackhammer.
- Crank Casey: A friend of Fender's who also lives at Aunt Fanny's boarding house. He is often pessimistic.
- Lug: A friend of Fender's who also lives at Aunt Fanny's boarding house. He can hardly find spare parts in his size.
- Diesel: A friend of Fender's who also lives at Aunt Fanny's boarding house. He does not seem to have a voice box but speaks through making sounds.
- Aunt Fanny: A kindly motherly figure to the Rusties who took them in when they were homeless.
- Cappy: Rodney's girlfriend and a Rusty sympathizer, who helps them defeat Ratchet.
- Bigweld: The former head of Bigweld Industries who, after being inspired by Rodney, helps the Rusties defeat Ratchet and starts manufacturing spare parts again.