Ireland and Crawford acted in Queen Bee, which was about 6 or 7 years prior to "I Saw What you Did." There was a famous quote of Crawford's where she claimed John popped a "pickle in his pocket" whenever they embraced on film!

I see on the Turner Classic Movies site that they confirm an affair between the two stars during the making of QUEEN BEE.

Another scary aspect of I SAW WHAT YOU DID, given the age of the female characters, is that Ireland had, at age 45, an affair with 16 year-old Tuesday Weld.