When Sheldon learns of the potential breakup, he enters "panic mode" to preserve his social structure.

Back on Earth, Raj brings Stuart into the fold to fill the "Howard-shaped void." Sheldon only accepts the change if Stuart agrees to behave exactly like Howard—Raisinets and all. Standout Quotes

This episode is a favorite for many because it balances the usual comedy with a deeper look at the Sheldon-Leonard-Penny "triad". While some viewers find Penny’s recurring doubts frustrating, others appreciate the series showing that Sheldon actually cares about Leonard’s happiness, even if he frames it as wanting things to remain "unchanging".

Things aren't going smoothly on the ISS. Howard is being relentlessly teased and even receives the first-ever "space wedgie" from his fellow astronauts.

(on marriage to Howard) "I'm basically married to a sexy Buzz Lightyear." The Fan Verdict

"I was expecting us to be an intimate group of five. Now, we're going to be a faceless mass of six."