Season 3, Episode 8 of The Big Bang Theory, "The Adhesive Duck Deficiency," features a dual plot where Sheldon aids a injured Penny while the other guys get high on laced cookies in the desert. The episode is famous for scenes featuring the "Soft Kitty" song and Sheldon revealing the meaning of Penny's tattoo. Watch the episode on Apple TV . The Adhesive Duck Deficiency | The Big Bang Theory Wiki