See, it's good you mention that. The OP on this site used the wrong word by calling it a "saying," at least by the dictionary sense. But his examples point to two-word usages that are well known, more or less.
(I get the "Jedi Clampett"--Jed/Jedi, by the way).
From the sister site, the idea is to complete two words that are known (green bean, alpha particle, monster truck, danger zone)--things we know of.
I'm pretty laid back, don't want to rock the boat. If that's the way you play, I'll adjust. It's good to know where you guys are coming from.