I mean, both shows were airing concurrently on ABC. Both shows were also from the same production company, D.L. Taffner Productions (https://www.dltentertainment.com/Distribution/USA/188), and both were based (https://www.threescompany.com/about/) on British shows (Man About the House (https://en.wikipedia.org/wiki/Man_About_the_House) and Keep it in the Family (https://en.wikipedia.org/wiki/Keep_It_in_the_Family_(1980_TV_series)) respectively).

Sure why not!

I think Larry went out of town (Santa Monica) to visit SF so it could have worked.

Didn't Chrissy go there with her boss?

Yeah it would've been fun to see Jack Tripper date one of the Rush girls even for just one episode. Of course Henry Rush would've been overprotective.

Fun fact John Ritter played the priest that married Ted Knight's character, Ted Baxter, on "The Mary Tyler Moore" show before he got the Three's Company gig.

Joyce Dewitt starred in this (https://www.reddit.com/r/threescompany/comments/1r4mc7b/joyce_dewitt_starred_in_this_preview_special_of/) preview special of CBS' Saturday morning cartoons in 1984. Co-starring Ted Knight!

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