Season 5, Episode 8 - The Isolation Permutation
Aired November 3, 2011
Amy's feelings are hurt whenr Bernadette and Penny go shopping for wedding dresses without her, forcing a reluctant Sheldon to comfort her.
Season 9, Episode 9 - The Platonic Permutation
Aired November 19, 2015
Sheldon and Amy try hanging out as friends when they spend Thanksgiving together at the aquarium. Also, Wolowitz reluctantly agrees to volunteer at the soup kitchen with Bernadette, Raj and Emily, and Penny discovers that Leonard knows more about her than she thought.