Episode Titles: Diffusion
You are viewing a list of 1 The Big Bang Theory episode featuring "Diffusion" in their title.
Season 5, Episode 9 - The Ornithophobia Diffusion
Aired November 10, 2011
Leonard and Penny spend time alone together as friends for the first time. Meanwhile, Sheldon is forced to overcome his fear of birds after one nests outside his apartment window.