Actor Gary Hudson, who played ABC head Tony Thomopolous, actually appeared on an episode of Threes Company. He appeared in the season seven 1982 episode "The Brunch."
Because 'Three's Company' was an ABC show, and this movie aired on NBC, many details had to be changed in order to avoid legal issues.
When executives are pitching the show to CBS, an actual clip from Man About the House (1973), the original British series, is used.