The Alley Cats are the main antagonistic group in Stuart Little. They are mafia-like stray cats who live in the streets and work for their boss Smokey.
Smokey was voiced by Chazz Palminteri, Monty was voiced by Steve Zahn, Red was voiced by David Alan Grier, and Lucky was voiced by Jim Doughan. Whereas the unnamed gray cat is the only one who has no voice actor.
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. To get rid of Stuart, Smokey finds two mice (Reggie and Camille Stout) and sends them to pose as Stuart's long lost parents in order to take Stuart away from the house and bring him to Smokey. Reggie and Camille however reveal the truth to Stuart which leads to the latter going back to his real home. He then encounters Smokey and the alley cats, who chase 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 which causes the latter to leave. Monty then tells Snowbell about their true intentions to eat Stuart, but Snowbell suddenly has a change of heart. The alley cats chase Stuart into Central Park where Snowbell appears to his assistance and snaps the branch that causes all of the alley cats (except Smokey) to fall into a river below. They then flee the scene humiliated leading to Smokey's defeat and possible death. None of them appear in the rest of the 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 redeemed.