During his reseach on flag information for his show "Fun with Flags", Sheldon finds out that during the 1936 Summer Olympics, Liechtenstein did come to the realization that its flag was identical to the flag of Haiti. Because of this finding, the government added the prince's crown to the canton. This change served two purposes, to signify Liechtenstein's position as a principality, and to "distinguish" its flag from Haiti's. This modified design was adopted on June 24, 1937.
One of the questions that Sheldon poses at the start of his "Fun with Flags" video blog is which is the only non-rectangular flag. The answer is Ohio which is pennant shaped. There are actually three countries with non-rectangular flags which are Switzerland And Vatican City with square shaped flags, and the flag of Nepal, which takes the form of two triangles placed one on top of the other, similar to a double pennant.
The flag on the right side of Sheldon and Amy's video is the apartment flag that Sheldon had made and is first seen in "The Staircase Implementation".
One of the items on Penny's bug report to Leonard is to be quieter during kissing. This is not the first time this complaint has been made - while dating Priya, Leonard was told "We're kissing, not eating hot soup" in The Roommate Transmogrification (2011). It has also been suggested in several episodes that Leonard can be quite noisy during sex.
This episode was watched by 16.13 million viewers with a rating on 5.5 in adults 18-49, and it was the first scripted series to beat American Idol in total viewers and adults 18-49 ratings since Friends ended in 2004.