The lowest rated episode of the series. (as of November 2016)
Penny's wedding dress is the same color as Kaley Cuoco's when she got married - pink. Ironically, after this wedding episode, Cuoco announced her divorce from Ryan Sweeting.
Sheldon mentions watching the Lord of the Rings trilogy with Amy for nearly 11 hours. The original theatrically released films in the trilogy clock in at a total of almost 9.5 hours, so Sheldon and Amy must have been watching the extended editions, which amount to almost 11.5 hours. Assuming that Amy insisted on skipping the lengthy end credits (undoubtedly to Sheldon's annoyance), they probably got to a running time of nearly 11 hours.
During their wedding, Penny quotes "You've Got a Friend In Me" from Toy Story (1995). The actress who plays Sheldon's mother is Laurie Metcalf, who also plays Andy's mother in Toy Story.
When Leonard talks about particles that have existed for 14 billion years since the universe began, he is referring to the Big Bang theory, the event in which all the parts of the universe were supposedly created, and which gives the show its name.