: While hosting the party, Leonard and Penny argue over the date of their first kiss. Leonard remembers it happening at a Halloween party years prior, while Penny insists it was at his birthday party.
The identifier "711-S12-E06-TBBT" refers to Season 12, Episode 6 of , titled "The Imitation Perturbation" . Watch 711-S12-E06-TBBT
The Imitation Perturbation | The Big Bang Theory Wiki | Fandom : While hosting the party, Leonard and Penny
: Penny eventually admits she does remember the Halloween kiss but wanted to "erase" it because she was drunk and only did it to make her ex-boyfriend, Kurt, jealous. She prefers to count the birthday kiss as their "official" first because it was the first time she kissed him because she truly cared for him. Costume Summary Initial Costume Party Costume Sheldon Doc Brown ( Back to the Future ) Howard Wolowitz Amy Clara Clayton ( Back to the Future ) Bernadette Rostenkowski-Wolowitz Howard Sheldon Cooper Bert the Chimney Sweep Bernadette Mary Poppins Leonard Inspector Gadget Inspector Gadget Raj Ruth Bader Ginsburg Ruth Bader Ginsburg Penny German Barmaid The Imitation Perturbation | The Big Bang Theory
: Howard Wolowitz decides to dress up as Sheldon Cooper for Halloween at Caltech. Sheldon is initially oblivious, but once he realizes everyone is laughing at his personality quirks—rather than with him—he feels deeply insulted and hurt.
: The mocking hit a nerve with Bernadette, who admits she has always felt she needed to be "tough" to be taken seriously due to her small stature. Sheldon and Bernadette eventually bond over their shared history of being bullied as children—Bernadette for her size and voice, and Sheldon for his intelligence. The First Kiss Dispute