Acting for Two: Ellen Travolta played Charles' mother Lillian and her character's own sisters Vanessa and Sally in separate episodes; however, neither character appeared on-screen at the same time.
Nicole Eggert played Jamie Powell and her cousin Amanda in the episode "Fair Exchange", again both characters never appeared in the episode in the same scenes.
Dawson Casting: Averted with most of the pre-teen/teenage cast members, the oldest of any of the Powell or Pembroke children in the series (in real life) was Nicole Eggert (born in 1972), who was never more than a year older (at the very least) than her character Jamie.
Played straight with Scott Baio and Willie Aames, who were in their mid-20s (although, it is assumed that Charles and Buddy are supposed to be college freshmen in the first season); the year-and-a-half gap between seasons one and two left Baio and Aames still playing college students (presumably seniors, though the slowed timeline and the lack of mentions of their characters' advancement in school make this unclear) while they were right around 30 in the fifth and final season (both were born in 1960, the series ended in 1991).
A double inversion in season five's "There's a Girl in My Ficus": Tiffani(-Amber) Thiessen plays a girlfriend of Charles in that episode. Thiessen however, was 16 when that episode was broadcast in 1990, Scott Baio was almost 15 years oldernote It's particularly puzzling when you consider that at the time episode aired, Thiessen was playing high school student Kelly Kapowski in Saved by the Bell, and also the fact that by Charles in Charge's fifth season, Charles was still supposed to be a college student.
Directed by Cast Member: Scott Baio directed 36 episodes, most of which were during the fourth and fifth seasons; in these instances, he is credited as a director under his (partial) full name, Scott Vincent Baio.
The Other Darrin: Jill Pembroke was originally played by Julie Cobb in the first season, however the role was recast with Lisa Donovan for the character's final appearance in the second season premiere "Amityville" (the first episode of the syndication run). It's odd when you consider that Michael Pearlman reprises his role as Jason Pembroke in that same episode.
Romance on the Set: By most reports, Scott Baio and Nicole Eggert dated towards the end of the show's run (by this point, Eggert was barely a legal adult, although not more than a year or two older than her character Jamie, who was still in high school in the final season).
Written by Cast Member: Willie Aames is given a "story by" credit in the season four episode "Buddy's Daddy".note The episode in which Buddy's father visits when he and his mother have marital problems. Scott Baio also wrote an episode.