Season 1 Edit
Jimmy is first introduced in the Pilot showing him watching Fiona as she and Veronica Fisher danced in a club. He watched from afar and tried to retrieve her stolen purse... but fails miserably. Endeared by his attempt at heroism, Fiona invites him back home to patch up the injuries he sustained while trying to retrieve her purse. Jimmy is initially enchanted by the Gallaghers as he notices the stark differences between their blatant poverty and his own affluent background. He is fascinated by Fiona and the Gallagher's lifestyle and initially seems to believe he can easily acclimate to their lifestyle, trying to seamlessly fuse himself into the family almost right away.
Fiona initially was uncomfortable and intimidated by Jimmy's background and afraid of falling for someone like him and during a phone call it is revealed that Jimmy has been watching her for a while, watching her from across bars and clubs, establishing that he has been enamored for some time.
Though he tries to assimilate into the Gallagher family in multiple moments it becomes abundantly clear that Jimmy and Fiona come from different worlds. A childhood friend of Fiona's, Tony Markovich, chases Jimmy away threatening to arrest him for his occupation of stealing cars unless Jimmy agrees to leave and never come back. Jimmy tries to tempt Fiona into escaping with him to leave her responsibilities behind for a life of leisure with him, but in the season finale Fiona decides to stay after all and Jimmy leaves the country alone.