When Jimmy first appears in the series (in the season two premiere), he is looking for his sister at the Tanner household when he comes across Stephanie playing a song on her guitar. Jimmy likes the song and sits down to visit with her. They kiss, and then Kimmy sees them. Stephanie is stunned when Jimmy does the Gibbler gallops with Kimmy, and that is when Kimmy reveals that Jimmy is her younger brother. Stephanie is shocked and horrified that she had kissed a Gibbler.
At D.J.'s super fun barbecue party, Kimmy asks Jimmy to pretend to be D.J.'s boyfriend, but Jimmy has a hard time keeping up the facade because he has feelings for Stephanie. Stephanie initially rejects Jimmy, but she eventually gives him a chance and goes on a date with him in his trailer, although she thought that he was going to take her to a fancy restaurant. Stephanie finally faces the fact that she has feelings for him.
In "Nutcrackers" (2.12), their relationship hits a small roadblock when Jimmy is offered a job in Oakland, California (though he keeps mispronouncing Oakland as Auckland), and also mentions that he loves her, which overwhelms her and causes her to avoid him. Jimmy leaves with his RV, making Stephanie, with D.J.'s help, examine their relationship. He returns on Christmas, surprising Stephanie when he shows up with presents that he bought at "Hanukkah prices".
- At 13 years old (S3, E8 of Full House), Kimmy says her parents stopped having kids after her, so if Jimmy was born after this, they would be more than 13 years apart (which is actually closer to the actor's age)
- Jimmy's RV is named the Gibbler Galloper (S2, E2), and he had a fryer put in because the RV does not fit through a drive-thru
- In the Fuller House episode "President Fuller" (S4, E7), Stephanie says that Jimmy is 28 years old. He then says he has a clown booked for next March (2018; known because Christmas '17 had just passed) – This would make him 11 years younger than Kimmy who was born on November 29, 1977
- made up the compliment "Rad-adj", pronounced radish, meaning Rad Adjacent (S2, E1 of Fuller House)
- has a U.S. centric map of the world, pinned with every place he's taken photographs (S2, E2)
- had his photos in Nation Geographic (S2, E2)
- "create[d] the illusion of a ghost using an elaborate series of pullies, levers, and electronic devices" (S3, E5)
- can solve a Rubik's cube and play the flute (S3, E9)
- is the paternal DNA of three viable embryos (S3, E12)
- is a nickname for James (S3, E12)
- is going to be a father (S3, E18)
- Is a father (S4, E13)