During the course of its run, The Big Bang Theory featured four Valentine’s Day episodes. If you wish to watch all the episodes simply follow this list:

• The Large Hadron Collision – The Big Bang Theory: Season Three, Episode Fifteen (2010)
• The Tangible Affection Proof – The Big Bang Theory: Season Six, Episode Sixteen (2013)
• The Locomotive Manipulation – The Big Bang Theory: Season Seven, Episode Fifteen (2014)
• The Valentino Submergence – The Big Bang Theory: Season Nine, Episode Fifteen (2016)

The Large Hadron Collision – Leonard is going to Switzerland to observe the Large Hadron Collider and is planning to take Penny for a romantic Valentine’s Day experience, but Sheldon has other ideas about who should be going with him. Penny gets the flu and ends up giving the flu to Sheldon and they take care of each other, while Leonard takes Raj to Switzerland – and the latter enjoys all the chocolate!

The Tangible Affection Proof – Leonard, Penny, Howard, and Bernadette go to dinner for Valentine’s Day while Sheldon and Amy search for the perfect gift for each other. Stuart and Raj plan a party for individuals who are not in a relationship at the Comic book store.

The Locomotive Manipulation – For Valentine’s Day, Amy plans a romantic weekend trip to Napa Valley on board a vintage train accompanied by Howard and Bernadette. Leonard and Penny opt to stay home, but have an accident while watching Cinnamon for Raj.

The Valentino Submergence. Amy and Sheldon host a Valentine’s Day edition of Fun With Flags; Penny and Leonard wrestle with getting older; Howard and Bernadette make a discovery in their hot tub; Raj is torn between Emily and another woman. Content collapsed.