Worked in a theatre in the early 80's, we had fantastic popcorn.
Don't know what it was, but does sound a lot like the flavocol everyone mentions. Popped our own in one of those movie style kettles with the spinning arm and the lids that lifted as the kettle filled.
Whatever we used came in sticks like butter, but was orange and solid at room temp (obviously not to healthy). Toss in one of those and about two cups of kernels and it was great popcorn that came out. Not sure if it's made any longer, or maybe a commercial product you can't even buy, but I tried for years to copy it's flavor and never came close.
Eventually switched to five gallon buckets of the stuff. Had an immersion heater/pump built into the top, so just pushed a button and added the corn. Still just as good.