The title is a reference to the movie Lost Boys. Katherine is the first 'lost girl' as she is being chased by Klaus and has nowhere to go and Vicki is the other 'lost girl' because she has just turned into a vampire and is 'lost'
Damon said to Elena, "Fool me once, shame on you."
The whole expression is "Fool me once, shame on you. Fool me twice, shame on me", meaning that once you have been fooled once, you should watch it that you are not fooled a second time.
Damon was actually fooled twice by Katherine. She makes him think that she burned inside Fell's Church. Later she makes him believe that she was locked in the tomb. He waits 145 years for the return of the comet to free her, only to find out that she was not inside the tomb either.
Frederick compelled Miss Gibbons not to let Damon in the house, but she should have, so that Damon, Alaric and Elena could rescue Stefan, meaning she was letting the wrong vampire into her house (Frederick).
Alternatively, it could be viewed as a reference to Swedish writer John Ajvide Lindqvist's vampire novel, Let The Right One In , published in 2004, or the original 2008 Swedish film based on and named for the novel, which was remade in English under the title Let Me In in 2010.
Stefan and Damon both drank blood in this episode to become vampires, thus the title "Blood Brothers" means that they had both drunk blood and now liked drinking blood. Blood brothers is also a reference to 2 people cutting themselves and clasping hands thus shairng blood, in order to become a vampire you need vampire blood in your system and Stefan and Damon both had Katherine's blood in their system and they are brothers.
Blood brothers also alludes to the play of the same title, where the two brothers end up killing each other. Interestingly, in the books, Damon and Stefan killed each other during a sword fight.
A quote from Shakespeare's The Tempest, and a book by Aldous Huxley about producing human clones. In the prequel novels to the Vampire Diaries, Damon says to Stefan, "Let's go see this brave new world." It is also about Caroline's new life as a vampire and her new view of things.
This episode revolves around and explains the past of Katherine Pierce, whose original name was Katerina Petrova. It details how Katherine has changed over the years, from her name, to her style, to her behavior.
In the episode there is a lot of explanations about the curse and the sacrifice. The main characters all make sacrifices to save another (Bonnie is willing to potentially kill herself with her magic to keep Elena from being sacrificed by getting the moonstone from the tomb and Katherine, Jeremy goes in the tomb to get the moonstone to stop Bonnie from using magic that could kill her, Stefan gets stuck in the tomb to save Jeremy, Elena tries to stop Klaus from coming to Mystic Falls, Damon stops Elena from giving herself over to Klaus, Elijah saves Elena and Damon from Klaus' men.)
The expression "daddy issues" refers to a woman (or man) who has a tense relationship with her/his father, or the father was absent during childhood. This episode Elena has to deal with her relationship with John, whom she always hated, but who is her biological father.
Damon throws a dinner party in this episode, where Alaric kills Elijah.
Guess who is coming for dinner " is a 1967 movie about a young woman introducing her family to her high educated and well manered black fianceé. The events of the movie also take place during a dinner party.
This episode features a Sixties Decade Dance, as well as the use of the quote, "Save the last dance." It is also the last dance before 'the sacrifice' takes place and seems to be Bonnie's last dance, when she fakes dying.
"The Sun Also Rises " is the title of a book by Earnest Hemingway. It also means that, despite everything that happened (John and Jenna's death and the sacrifice ritual), we need to find hope and strength to move on.
Damon lay dying in this episode but was rescued by Klaus' blood which Katherine brought to him. It is also the title of a book by William Faulkner, that is ranked among the best novels of the 20th century. The title of the book is derived from a frase from "The Odissey ". "As I lay dying, the woman with the dog's eyes would not close my eyes as I descended into Hades."
Rebekah notices that Stefan is acting strange, so she tells Klaus, and Elena's friends (Alaric, Caroline and Bonnie) start to point to Damon and Elena's relationship is considered "disturbing behaviors" to them.
It's the name of a 1998 thriller about three outcast students who are horrified by the actions of their "blue ribbon" classmates.
Homecoming is an American tradition, where alumni are invited to return to their Alma mater, usually for a special Football game. Normally there are several activities including a parade, cultural events and decade dances.
Elena is invited to a dangerous ball where Esther will tell Elena about a dangerous plan to kill Klaus and her other children.
It's also a reference to the novel "Les Liaisons Dangereuses" by Cholerdos de Laclos, that originated a play with the same name by Christopher Hampton, which inspired the movie Dangerous Liaisons directed by Stephen Frears and another one named Cruel Intentions, starting Sarah Michelle Gear, Reese Whiterspoon and Ryan Phillippe.
A reference to the death of Finn and his entire bloodline of vampires, including Sage. The title could also mean that the murder of an Original could result in the death of the many vampires they created.
A Murder of One " is a song from the band Counting Crows The name of the band came from a line from this song. A group of crows is called a "murder", so a murder of one is a group of only one crow.
Elena has to be rescued before sunset, since daylight is what is keeping Alaric trapped at school, as he can not go out into the sun.
Before Sunset " 2004 movie, sequel to "Before Sunrise", with Ethan Hawke and Julie Delpy. A couple who has spent one night together 9 years ago spend one afternoon together. The movie plays in real time.
Like all people with a conscience, Elena goes a little mad after killing Connor. Also, she was being haunted by the cursed ghost of Connor.
We All Go A Little Mad Sometimes is a direct quote for the movie Scream, which Kevin Williamson wrote. It was his first film and launched his career. It was also quoted in both versions of the movie Psycho (1960 and 1998).
The name of the episode is a play on "We'll Always Have Paris" - a famous quote from the movie Casablanca. It refers to the memories of the good time they spent together in the past, although they have been separated now.
Bourbon Street refers to a street in New Orleans, where Damon left Charlotte, and after 70 years he found her again.
Is a 2007 Biographical film of Christopher McCandless who lived in the Alakan wilderness who die while living in a bus he drove. Its an refernce to the gang being on the island where they encounter death with Jeremy being killed by Slias.