The production of this series caused tension on the set of Vivre à trois (1976) between John Ritter and the rest of the cast. The producers tried to keep it a secret from the rest of the cast. But they eventually found out and were disappointed that the series would essentially continue without them.
Don Knotts was offered a recurring role but turned it down. Suzanne Somers lobbied to reprise her role as Chrissy but was turned down.
The pilot of the British series Man About the House (1973), which Three's Company was based on, was entitled Three's a Crowd (1984).
The series originally planned to star Richard Kline reprising his role of Larry from Vivre à trois (1976). Kline was then offered a recurring role in the series which he turned down.
It was never revealed what the initials E.Z. stand for in the character E.Z Taylor's name, Jack's assistant chef.