Season 7, Episode 24 - The Status Quo Combustion
Aired May 15, 2014
With his career in flux Sheldon struggles to deal with even more changes in his life, leading him to make a drastic decision. Meanwhile, Raj and Emily's relationship takes a step forward, while an injured Mrs. Wolowitz puts a strain of Howard and Bernadette's life.
Season 8, Episode 23 - The Maternal Combustion
Aired April 30, 2015
When Sheldon and Leonard receive an award for the paper they co-wrote together, their mothers both pay a visit to Pasadena. Meeting for the first time, sparks fly between Mary Cooper and Dr. Beverly Hofstadter when they don't see eye to eye on religion or psychiatry.
Meanwhile, Bernadette has had enough of feeling like a mother to three teenage boys, so Howard, Stuart and Raj are told to clean the kitchen.
Season 9, Episode 21 - The Viewing Party Combustion
Aired April 21, 2016
Everyone must choose sides when a small argument between Leonard and Sheldon erupts into a heated fight during a group get-together.