Lucky Jack was present in early drafts of the film when it was supposed to be a supernatural western called Sweatin' Bullets. Assisting the calf protagonist in saving his herd from the ghostly Alameda Slim and the Willies gang, it would have been revealed that Slim took Lucky Jack's foot as a charm.
Lucky Jack is very friendly and laid-back, but his name contradicts his good fortune. This is proven when he gets tortured by predators or other critters, accidentally sets his peg leg on fire, and kicks at a cactus with Alameda Slim's wanted poster on it, getting thorns in his foot. Aside from these misfortunes, Lucky Jack is very helpful and reliable when it comes to assisting other animals, especially cows.
Lucky Jack is first seen waking up in his hole in the desert, where he is then chased by a coyote. Jack then runs into a chuck wagon after losing the coyote and tries to run away from the wagon, but his ears get caught in one of the wagon's wheels. He is then sent flying into a cattle drive, where he is poked by the sharp horns of the cattle, and is again hurled into an owl's nest. The owlets painfully peck him continuously, and he flees while being chased by the owlets. He then hides underneath an animal's skull, but when he throws it away, a rattlesnake is seen on his face. Upon realizing the rattlesnake on his face, Jack panics and then runs away.
Later, when Maggie is being sent to Little Patch of Heaven by her former owner, Jack, with the rattlesnake still on his face, continues running until he bumps headfirst into a cactus, knocking the rattlesnake off his face.
Jack has a bigger role later in the film, when he meets Maggie, Mrs. Calloway and Grace and brings food to them while they were asleep. He then introduces himself to the cows and offers them a scorpion which they decline, as they were on a quest to catch outlaw Alameda Slim in order to save Little Patch of Heaven due to financial trouble. Jack understands and tells them that he too once had a home called Echo Mine, where he and other jackrabbits used to live, until Slim forced them all out and made the mine his hideout. Eager to get revenge on Slim, Jack leads the cows to Echo Mine. When the bovines find and capture Slim, Lucky Jack smacks the outlaw in the face with a mining pan. He also uses the pan to battle the Willie Brothers when they ambush the cows.
In the film's climax, Jack defeats one of the Willie Brothers by throwing a horseshoe from Buck at him, knocking him out. Later, Jack, Buck and the cows hijack a train to get home, but it gets in the path of another oncoming train. When the switch that reverses the train track breaks, Buck, thinking fast, wedges Jack's wooden peg leg in the switch's opening and pushes him down like a lever, thereby saving the cows from a possible collision while the driver of the oncoming train yells, "Roadhogs!" Jack tries to pull his peg leg out of the lever while he and Buck wish the cows good luck, and the two eventually arrive at Little Patch of Heaven after Slim is arrested when his disguise is removed.
Jack is last seen on Little Patch of Heaven with Jeb as his new friend and roommate. Jack reads a newspaper about the cows' heroic feat in capturing Alameda Slim, but Jeb chews up the article before Jack can finish reading it. Jack scolds Jeb for chewing the paper, and Jeb tries to force Jack out of his barrel, and the two both start fighting. As they fight, the barrel they live in rolls around. Later, the barrel with Jeb, Jack, and Rusty falls into the water trough, with all three of them laughing at the end.
- Lucky Jack bears a great resemblance to the March Hare from Alice in Wonderland.
- In the original version of Home on the Range, he was supposed to be the deuteragonist before the script changed.