Jack was once a powerful bouncer from Las Vegas who was known for his unstoppable fists. He earned the nickname "Cracker", due to the baseball bat he always wielded. When a certain criminal organization decides to go after Jack for unknown reasons, he decides to elude them by becoming the bodyguard of Blair Dame, the daughter of a wealthy European family, when she decided to travel the world.
Jack disappeared after the trip was over, only to reemerge when an underground fighter named King Bharat kidnapped his younger sister. Jack defeated Bharat and rescued his sister, only to be pursued again by the organization he was eluding. Eventually he was forced to go to Blair's mansion to hide there for a while.
Of all the Street Fighter EX characters whose backstories were changed, Cracker Jack was one of the most drastic. In the first game, he was a Shadaloo enforcer who preferred working alone. He acts as a drill sergeant (a duty he takes offense to) and teaches inexperienced grunts how to deal with pain and recover from serious injuries. This has been retconned to his current storyline.
Though a member of Shadaloo (in his original backstory), Cracker Jack seems to have betrayed the organization, as he destroys a Shadaloo train in his ending.
Cracker Jack's fighting style is similar to Balrog's, though he can kick and also wields a baseball bat.