One of the most discussed moments among fans is Penny's invitation for "coffee," which Stuart famously takes literally, much to Penny's amusement.
"The Big Bang Theory" The Hofstadter Isotope (TV Episode 2009) - IMDb [S2E20] The Hofstadter Isotope
The episode highlights Sheldon’s social oblivious nature, as he inadvertently ruins Stuart’s chances of sleeping with Penny by refusing to drop a comic book argument. Production & Reception One of the most discussed moments among fans