Howard learns that he's going up to the Space Station earlier than originally intended, which unfortunately puts a crimp in his wedding plans with Bernadette. Amy tries to take her relationship with Sheldon to the next level. Also, Leonard makes a very awkward declaration while having sex with Penny.
- Behavioral Conditioning: Amy tries to advance her relationship with Sheldon by associating herself with things he likes. For example, she serves him his favorite foods while playing the theme to Super Mario Bros. in the background.
- Continuity Nod: Sheldon's favorite meal - spaghetti with little hot dogs - was already mentioned back in Season Three's "The Spaghetti Catalyst".
- Playing Doctor: Amy tries to get Sheldon to play doctor... Star Trek style.
- Stock Underwear: Sheldon wears long johns while trying out rental tuxedos for hygienic reasons.
- Wrong Name Outburst: Leonard doesn't say anyone's name, but he says something just as embarrassing: he proposes.
- Your Favorite: Amy serves Sheldon his favorites: spaghetti with little hot dogs and Strawberry Quik.