Valentine's Day has led to some great episodes of TV. These may not be the best examples, but they are the ones I remember the most.
1. Buffy the Vampire Slayer - "Bewitched, Bothered and Bewildered"
In one of Buffy's best-ever episodes, a spell gone wrong causes every woman in Sunnydale (but Cordelia) to fall in love with Xander. As the spell gets stronger, Amy the Teenage Witch turns Buffy into a mouse, and Buffy's mom hits on Xander. Most holiday-appropriate: Cordy calls Harmony a sheep and gets back together with Xander.
2. Lost - "The Constant"
Airing last year on Valentine's Day, "The Constant" is already a Lost classic. Heading out to the freighter, Desmond catches time travel sickness and gets dislodged in time. The only thing that can keep him alive: his Constant, true love Penny Widmore. When Penny answers the call on Christmas, she doesn't just save Desmond's life, but creates the show's most romantic moment.
3. The Simpsons - "I Love Lisa"
I choo-choo-choose you. Ralph's misguided crush is elementary school Valentine's Day at its most embarrassing.
4. Arrested Development - "Ready, Aim, Marry Me"
There's plenty of potential couples in this romantic getaway-themed episode to choose from - Lindsay and Uncle Jack (guest star Martin Short), Lucille 2 (Liza Minelli) and Buster, or Michael and Sally Sitwell. But the best one is Michael and Tobias. Tobias' self-recording leads to some of his best-ever unintentional double entendres.
5. Veronica Mars - "Ruskie Business"
Not much love for V in this episode. She helps new-friend Meg find her secret admirer....only to find out it's her ex, Duncan. She helps a Russian mail order bride find her husband...only to find out she's Russian mafya looking for someone in witness protection. Still, dressing up as Madonna for an 80s-themed dance? Awesome.