The Big Bang Theory
A full list of special holiday episodes

The Big Bang Theory
12 seasons, 2007–2019
The lives of two brilliant yet socially awkward physicists, Leonard and Sheldon, change when they meet their new neighbor, the beautiful and free-spirited Penny.
The show aired 6 Christmas episodes, 2 Thanksgiving episodes, 4 Halloween episodes, and 4 Valentine's Day episodes.
Christmas episodes:

Season 2, Episode 11
The Bath Item Gift Hypothesis
Leonard becomes jealous when Penny takes an interest in a handsome physicist at the university. Meanwhile, Sheldon struggles to choose the perfect Christmas gift for Penny.

Season 3, Episode 11
The Maternal Congruence
Leonard's mother pays a visit, much to Leonard's chagrin and Sheldon's excitement

Season 6, Episode 11
The Santa Simulation
The girls take Raj out to a nightclub to help him find a date. Meanwhile, a game of Dungeons and Dragons brings back memories of Santa Claus for Sheldon.

Season 7, Episode 11
The Cooper Extraction
Sheldon goes back home to Texas for the holidays. The absence of Sheldon causes the group to appreciate his unique personality and contribution to their friendships.

Season 8, Episode 11
The Clean Room Infiltration
Amy hosts a traditional Victorian Christmas Eve dinner for the gang, while Raj's father visits from India. The guys try to get rid of a bird they accidentally let into the university clean room.

Season 10, Episode 12
The Holiday Summation
The gang share stories about their holiday breaks. Sheldon and Amy talk about their trip to Texas, Leonard and Penny share their Christmas tree adventure, and Howard and Bernadette discuss their experiences as new parents.
Thanksgiving episodes:

Season 7, Episode 9
The Thanksgiving Decoupling
The gang decides to spend Thanksgiving at Mrs. Wolowitz's house, but Sheldon is unhappy about the holiday, and tensions rise when Penny's ex-boyfriend shows up.

Season 9, Episode 9
The Platonic Permutation
Sheldon and Amy try to spend time together as friends and visit an aquarium on Thanksgiving. Howard agrees to volunteer at the soup kitchen with Bernadette, Raj, and Emily.
Halloween episodes:

Season 1, Episode 6
The Middle Earth Paradigm
The guys attend Penny's Halloween party, but Leonard has a tense encounter with Penny's ex-boyfriend Kurt.

Season 5, Episode 7
The Good Guy Fluctuation
Sheldon tries to scare the gang after they play a prank on him for Halloween. Leonard seeks Penny's advice when an attractive comic book artist shows interest in him.

Season 6, Episode 5
The Holographic Excitation
Raj organizes Stuart's Halloween party at the comic book store while Howard's constant talk about space annoys the gang. Meanwhile, Penny makes an effort to take an interest in Leonard's work.

Season 12, Episode 6
The Imitation Perturbation
Wolowitz dresses up as Sheldon for Halloween and Sheldon seeks revenge. Leonard is surprised when Penny doesn't remember their first kiss.
St. Valentine's Day episodes:

Season 3, Episode 15
The Large Hadron Collision
Leonard is invited to visit the CERN laboratory in Switzerland on Valentine's Day, and Sheldon competes with Penny to be his guest.

Season 6, Episode 16
The Tangible Affection Proof
Sheldon enlists Alex's help to buy a Valentine's Day gift for Amy. Leonard, Penny, Howard, and Bernadette have a disastrous dinner together. Raj and Stuart host a "Lonely People" party at the comic book store

Season 7, Episode 15
The Locomotive Manipulation
Sheldon and Amy go on a train ride to Napa Valley with Howard and Bernadette for Valentine's Day. Meanwhile, Leonard and Penny take care of Raj's dog.

Season 9, Episode 15
The Valentino Submergence
Sheldon and Amy host a Valentine's Day edition of "Fun with Flags". Leonard and Penny come to terms with the challenges of aging. Meanwhile, Howard and Bernadette discover a surprise in their hot tub.