Season 2, Episode 22 - The Classified Materials Turbulence
Aired May 4, 2009
After Howard designs a special toilet for the International Space Station, the guys rush to develop a fix to stop the toilet malfunctioning in space. Meanwhile, Penny goes out on a second date with Stuart from the comic book store. When Leonard gets the impression things went awry on Penny and Stuart's date, he is thrilled to learn the reason why.
Season 6, Episode 20 - The Tenure Turbulence
Aired April 4, 2013
When a tenured position opens up at the university, Leonard, Sheldon and Raj compete with Barry Kripke for the job. The competition intensifies when the girls get involved and fight for their guys.
Season 7, Episode 17 - The Friendship Turbulence
Aired March 6, 2014
When a spat breaks out between Howard and Sheldon, Bernadette tries to bring peace to the group, leading Howard and Sheldon to fly to Texas together. Meanwhile, after Penny's car breaks down she wonders whether she'll have to get her job back at the Cheesecake Factory or take an embarrassing movie role. Raj seeks Amy's help in contacting a potential mate on an internet dating site.