^ Kondolojy, Amanda (November 8, 2013). "Thursday Final Ratings: 'Elementary', 'Scandal', 'The Vampire Diaries', & 'The Big Bang Theory' Adjusted Up; 'The Voice', 'The Millers', 'Sean Saves the World', 'Parenthood', & 'The Michael J Fox Show' Adjusted Down". TV by the Numbers. Archived from the original on November 8, 2013. Retrieved November 8, 2013.
In 2010, Leonard, Howard, and Raj mined a lot of Bitcoin, now worth thousands of dollars, but left Sheldon out due to his fear of tax implications. Flashbacks are shown of how the Bitcoin ended up on an old laptop of Leonard's, which Penny gave to her old boyfriend Zack after she and Leonard broke up. In 2017, Leonard and Penny retrieve the computer from Zack, who first shows them a video of a drunken Penny apologizing for breaking up with Leonard. The Bitcoin is not found on the laptop. Sheldon had moved it to a flash drive on Leonard's keychain to teach the guys a lesson, but Leonard lost the keychain years ago. A final flashback to 2013 shows Stuart discovering the flash drive, which he decides to erase and sell for $10.
When Leonard receives a braggy Christmas letter from his brother, he feels bad about how little he and Penny have achieved in the past year. Leonard wonders if he and Penny should be thinking about the next step after two years of marriage, like buying a house or having a baby. Penny tells him she wants to do all those things someday, but she has a bunch of stuff she would like to do first.