Love is in the air, as Leonard and Howard take Penny and Bernadette out for Valentine's Day (after Howard's brilliant plan to create a nano-Valentine goes awry). Howard and Bernadette are having a fight because he didn't do the laundry and she hid his X-Box, while Penny gets anxious seeing an ex-boyfriend and his new girlfriend out at the restaurant.
Sheldon solicits the help of his research assistant Alex to get a Valentine's present for Amy, but ends up coming up with a gift on his own that more than does the trick.
Raj and Stuart, with nothing to do, decide to throw a Valentine's Day party at the comic book store for those who have nothing better to do. Raj gives a motivational speech to the group about how they can stick together as a community and never be alone ... but then he meets a girl who seems interested in him, so he ditches those losers.
This episode actually had some real heartwarming moments between the various couples, so it was a nice change of pace, and hinted at some upcoming emotional development ... which may or may not actually occur.
This Episode's Science
Howard: I was trying to come up with something really romantic to give Bernadette for Valentine's Day, since she's been such a pain in the ass.
Leonard: Can't find a card that says that?
Howard: Check it out. I used the atomic force microscope in the material science lab and wrote our initials in a heart one one-thousandth the size of a grain of sand.
Leonard: [Looking into the microscope] Wow, that's cool.
Howard: A micro-Valentine for a microbiologist.
Leonard: From her micro-husband. That is amazing. How long did this take you?
Howard: About 12 hours. I pulled an all-nighter. Yeah, it really took a bite out of my video game time.