Jiji is Kiki's companion as she is training to become a full-fledged witch. One time, he has to pretend to be a stuffed cat for a boy's birthday gift. The real stuffed cat which looked exactly like him, was lost in the forest and Kiki had to go find it. This was during Kiki's first delivery.
Jiji also gets a girlfriend, a white cat named Lily. In the credits, it is revealed that Jiji and Lily had four kittens, with three bearing a close resemblance to Lily and one looking exactly the same as Jiji.
In the original Japanese script, Jiji is actually female.
Also a difference in the original Japanese, it is left ambiguous as to whether Jiji ever regained the ability to speak with Kiki.
The role was the final voice acting performance of Phil Hartman.
The original 1998 VHS release, which saw rerelease on both VHS and DVD in 2003, was full of ad libs and one liners provided by Hartman, as well as some banter between Jiji and Kiki, almost all of which were removed from the 2010 DVD and BluRay release. Fans of the movie are divided as to whether this completely ruined the movie or totally improved it, but they all seem to agree that it was somewhat disrespectful to Jiji's voice actor, Phil Hartman, as it was his last ever voice acting performance, and he was no longer around to do anything about these obvious dub edits.