Lucky is a cream and brown Siamese cat with multiple stripes.
Lucky was first seen when he asks Stuart Little where he's going and called him Murray and was chasing him in the roadster alongside Smokey and Red but they failed to get Stuart as he was going back to his home.
He was later seen again with Monty, Red, Smokey and the Unnamed Gray Cat and was seeing Stuart and Snowbell and then when Snowbell was almost breaking the branch he was standing with Red, Monty and the Unnamed Gray Cat and then the branch broke and all 4 of them were screaming and were defeated by Snowball and ended up falling into the water and Red was saying that he'd rather drown and Red escapes from the water with Lucky, Monty, and the Unnamed Gray Cat. Lucky emerges out of the water all wet and he shakes off his wet fur after he, Red, Monty and the Unnamed Gray Cat got defeated.
After Lucky gets defeated, he, along with Smokey, Red and the Unnamed Gray Cat were never mentioned or seen again in the rest of franchise but Monty was seen in the rest of the franchise.
Like the other alley cats, Lucky is snarky and evil. He does not appear to have the intelligence of Smokey and Monty, as evidenced by his failure to immediately realize that Smokey was referring to Stuart as the picnic. He does appear to be more intelligent than Red, as he seemed to be aware that Murray wasn't really Stuart's name.
Lucky's first scene
Lucky updates Smokey about Stuart's whereabout
"What's your hurry, Murray?"
Lucky, Smokey and Red
Lucky, Red and Smokey chasing Stuart
Smokey, Lucky and Monty
"He's hoggin' the mouse. He ain't sharin'!"
Smokey, unnamed gray cat and Lucky
Lucky and unnamed gray cat about to jump to another branch
Lucky chasing Stuart through the trees
"Look! It's mouse on a stick. I love mouse on a stick!"