Life in Pieces' John (James Brolin) and Joan (Dianne Wiest) are the epitome of cool parents--having proven themselves to be a pretty roll-with-the-punches duo. In this clip fromThursday's season finale, we learn they're a lot more cool (and progressive) than anyone ever knew, including their own daughter Heather (Betsy Brandt).

Nora Dunn guest stars as Carol, who used to be John's co-pilot back in the day, and is married to Karol, who was a stewardess (John's lovably retro term). The two couples are catching up and trading goofy jokes ("I remember I asked them to bring some nuts up to the cockpit" John says, " know, nuts were the last thing on their minds!") but the giddy reunion soon comes to a halt when Heather enters, and Carol inadvertently drops a bomb about John and Joan that shakes Heather to her core.

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It turns out that Heather's parents have been keeping a secret for 35 years and while it highlights how progressive they are — but it's definitely not cool to their grown daughter. What do they reveal? Check it out in the clip below.

Life in Pieces airs Thursday, March 31 at 8:31/7:31c on CBS.

(Full disclosure: is owned by CBS)