The kid who played Greg Brady was also in a TV series, Day By Day, which I don't think lasted too long but, in one of the episodes there was a dream sequence where the kid dreamt he was in The Brady Family. It was quite clever.
From Wiki:
"A Very Brady Episode"
The episode titled "A Very Brady Episode" aired on February 5, 1989, and reunited six cast members from The Brady Bunch – Ann B. Davis, Florence Henderson, Christopher Knight, Mike Lookinland, Maureen McCormick, and Robert Reed.
In this episode, Ross is lectured by Brian and Kate about his poor study habits. Ross's explanation that he was watching a Brady Bunch marathon only angers his parents more, and he is warned to shape up. Ross bemoans his predicament, noting Mike Brady would never yell at him because he had flagging grades.
Ross falls asleep, and finds himself in the opening credits of The Brady Bunch., where he dreams that he is the Bradys' long-lost son, Chuck. After he gets his hair permed at Mike's suggestion, he visits with the various family members (except Greg, Jan, and Cindy), who reprise some of the scenes in the Bradys' most famous episodes ("Chuck" and Marcia running against each other for class president, "Chuck" being bullied by Buddy Hinton episode, etc.)
After "Chuck" gets some advice about his poor grades from Mike, the family begins to repeat their dialogue. "Chuck" wonders what's amiss, and Carol explains what he's seeing is a rerun. Everything becomes chaotic and Ross wakes up, vowing to improve his study habits.
Christopher Daniel Barnes, who played Ross on the series, would later portray Greg Brady in The Brady Bunch Movie and A Very Brady Sequel.