They first appear after Monty introduces Snowbell to Smokey and makes a deal with him to get Stuart out of the house and kill him.
Smokey then sends two mice (Reggie and Camille Stout) to pose as Stuart's long lost parents to take him away from the house. Reggie and Camille however reveal the truth to Stuart leading to the latter going back to his real home. He then encounters the alley cats who pursuit him until he crashes his car into the sewers.
Stuart then escapes from them and heads back to the little house where he encounters Snowbell who lies to him that he's unwanted causing the latter to leave. Monty then tells Snowbell about their true intentions to eat Stuart causing Snowbell to have a change of heart. They chase Stuart into Central Park where Snowbell appears to his assistance and snaps the branch that all of the alley cats (except Smokey) are standing on causing them all to fall into the waters below.
They then flee the scene humiliated leading to Smokey's defeat and possible death. None of them appear in the rest of the Stuart Little franchise again with the exception of Monty.
- Monty is the only member of the Alley Cats to appear in the TV show and all 3 movies. Monty was also the only member of the Alley Cats to be reformed.