Season 4, Episode 13 - The Love Car Displacement
Aired January 20, 2011
When the gang stays in a hotel for a science conference, Howard and Bernadette have an argument after she runs into her ex-boyfriend which causes a ripple effect throughout the group.
Season 6, Episode 10 - The Fish Guts Displacement
Aired December 6, 2012
When Amy comes down with the flu, she calls on Sheldon to take care of her. After Amy enjoys Sheldon's care a little too much, she takes advantage of him as she gets better. Meanwhile, Bernadette tells Howard to join his father-in-law, Mike, for a fishing trip to get to know him better.
Season 7, Episode 7 - The Proton Displacement
Aired November 7, 2013
Sheldon feels snubbed when his idol, Professor Proton, seeks Leonard's help for a science paper instead of his. Sheldon gets his revenge by befriending rival science icon Bill Nye. Meanwhile, Howard's presence at girls' night irritates Raj, who feels he can only be himself around the girls.