Jackie is a thrill-seeking girl and a descendant of Calamity Jane. She appears in The Wilder West. Zack develops a crush on her which lasts only one episode - for he later realizes that she's crazy - and he doesn't want to follow her anymore.
Jackie didn't know about Murphy's Law, but found it fun to seek peril (increased by Milo's presence).
She calls Zack 'Boy Band' hinting that she might know about his previous enterprises with The Lumberzacks.
Jackie is one of only seven characters in season 1 who's eyes have pupils.