Season 6, Episode 3 - The Higgs Boson Observation
Aired October 11, 2012
Amy has feelings of jealousy when Sheldon hires a young female assistant, although she seems more interested in Leonard than Sheldon. Meanwhile, Howard's time aboard the International Space Station is beginning to take its toll.
Season 7, Episode 18 - The Mommy Observation
Aired March 13, 2014
When Sheldon stops by his mom's house in Texas, he must learn to deal with her new romantic status. Meanwhile, Raj throws a "Murder Mystery" party for the gang, leading to tension among the friends.
Season 9, Episode 8 - The Mystery Date Observation
Aired November 12, 2015
Sheldon, Wolowitz and Koothrappali post an online advertisement to find Sheldon a new girlfriend. Also, when Amy is coy with details about a guy she is dating, Penny and Bernadette decide to spy.