Writers Brian Cooke and Johnnie Mortimer were inspired to create "Man About The House" after noticing increasing numbers of advertisements in the London press for flatmates of either gender - until the early 1970s, it was usual for flatsharing households to be all male or all female.
In "One For The Road", it is discovered that Robin's middle name is Oswald. Chrissy points out that his initials spell the word ROT.
The success of this show led to two highly successful spin-off series for Thames/ITV: Robin's Nest (1977), in which Robin starts his own restaurant with his live-in girlfiend (Tessa Wyatt) and George & Mildred (1976) with Yootha Joyce and Brian Murphy, where the Ropers move to a new upmarket area.
Sally Thomsett (Jo) appeared in this just three years after playing an 11 year old in 'The Railway Children' (1970).
In season 5 episode one, "The Last Picture Show", Chrissy has her 22nd birthday. Considering that 3 episodes ago, in the Christening episode, she stated that she wasn't even 21 years old, at least a year has passed within the story universe between season 4 and 5. Its still unclear what ages the characters were, in season 1 episode one, entitled "Three's Company", confusingly named as the later USA series version, was named after the UK episode name.