In the second episode "The Junior Professor Solution" of the 8th season of the Big Bang Theory, there exists a brief moment where Sheldon Cooper references one of his boards with what for a brief moment looked like a bunch of statements in some formal system which has modal operators and quantification. But there also exists an "ess" phrase in one of the strings of symbols. I also couldn't tell what the rules of the system they would have referenced or what the axioms were.
Did the Big Bang Theory reference a formal system or just write symbols that looked like a formal system to an untrained eye (my guess is the later)?