* ActingForTwo:
** Paul Wesley is portraying Stefan, one of the three central protagonists. [[spoiler:In Season 4, it's revealed Stefan's ancestor is Silas and he is Silas' doppelganger. It's revealed in Season Five, there is one other doppelganger of Silas' alive in the present day, Tom Avery, an innocent paramedic.]]
** Acting for four in Nina Dobrev's case. She portrays Elena the protagonist, also Katherine a villain and one of the major antagonists. In Season Five Nina Dobrev also portrays Amara, the original Petrova, and Elena and Katherine are her doppelgangers. On the spin-off [[Series/TheOriginals]], she portrays Tatia in flashbacks to the 10th century and Katherine' is ''her'' doppelganger.
* ActorAllusion:
** Mia Kirshner, who plays a vampire, also starred in the early 90's series ''Dracula''.
** Jack Coleman plays [[Series/{{Heroes}} the father of a blond-haired girl with supernatural powers]]. He also hunts people with similar supernatural powers.
** David Anders was able to [[Series/{{Heroes}} come back from the dead before]].
* ActorSharedBackground: Katherine is originally Bulgarian, as is Nina Dobrev.
* CastingGag: Creator/PhoebeTonkin (Hayley) and Creator/ClaireHolt (Rebekah) were both main characters in ''Series/H2OJustAddWater''.
** Mia Kirshner, who plays Isobel Flemming, [[spoiler:Elena's real birth mother,]] played the role of a woman named Catherine in Film/{{Not Another Teen Movie}} (granted, spelled differently from our Katherine).
* DawsonCasting: The mostly teenage cast is played by actors in their 20s, making some casting choices downright bizarre. The actors who play the Gilberts are only one year apart, starting with Nina Dobrev (20), Steven R. Mc Queen (21), and [[PlayingGertrude Sarah Canning (22).]] And to top it off, [[Series/ADifferentWorld Whitley Gilbert]] (48) a grandma?!
** This is made extra weird by the casting of John Anders (born 1981) as [[spoiler: Elena's [[AbsurdlyYouthfulMother father]], John Gilbert.]] Isobel, who is supposed to be younger than him even without being a vampire, is played 35-year-old Mia Kirshner.
** Justified in the case of Jasmine Guy as "Grams" Sheila Bennett; she's meant to have preternatural longevity as a witch. Stefan mentions first meeting her at a protest rally in the 60s, though he's not sure she would remember. She did.
* FakeAmerican:
** Elena is played by Bulgarian-born Canadian Nina Dobrev
** Several of the originals (at least Klaus, Rebekah, and Kol plus the dead son Henrick) were born in the New World, making them and are not played by American actors
** American Hayley Marshall is played by Australian actress Phoebe Tonkin.
* FakeNationality:
** Hispanic Michael Trevino plays the white Tyler Lockwood who is descended from Native Americans.
** The Salvatores are Italian-American, neither Paul Wesley nor Ian Somerhalder are Italian, neither does James Remar who plays their father.
* HeyItsThatGuy:
** Anna is [[{{Unfabulous}} Geena Fabiano]].
*** Her mother is played by Creator/KellyHu.
** [[Series/{{Heroes}} Adam Monroe]] is Elena and Jeremy's uncle, [[spoiler: as well as Elena's birth father.]]
*** Another one for ''Series/{{Heroes}}'' fans: Noah Bennet is Caroline's dad.
*** Gretchen is the [[spoiler: first vampire to be sired to Damon]].
** [[Series/TheLWord Jenny Schecter]] is Alaric's wife and [[spoiler: Elena's birth mother.]]
** Bonnie's Grandma is [[Series/DeadLikeMe Roxy]].
** Rebekah is [[Series/H2OJustAddWater a mermaid]].
*** She's also [[Series/PrettyLittleLiars Samara]].
*** And an [[HilariousInHindsight ironic twist]], Maya is Bonnie's ancestor, Emily.
*** Plus, Melissa's no longer dating a doctor, now that she is one.
** Hayley is also [[Series/JustAddWater a mermaid]]. And [[TheSecretCircle Faye Chamberlain]].
** Sarah, [[spoiler: the girl Tyler kills]] is [[CoryInTheHouse Meena]].
*** Also, she's [[Series/DesperateHousewives Ana Solis]].
*** Her best friend that Katherine kills is [[Series/SuiteLifeOnDeck London Tipton's former roommate]].
** Caroline's mom is [[Series/KyleXY Nicole Trager]].
** Sage is [[Series/{{Smallville}} Tess Mercer]].
** Stefan was [[Series/AmericanDreams JJ's friend]] and [[Film/{{Fallen}} an angel]].
*** He was also Sage's [[spoiler:[[Series/{{Smallville}} half-brother Lucas]]]], even though they never appeared on-screen together.
** [[Series/{{Degrassi}} Mia]] is now torn between vampires.
** So Tyler used to be friends with [[TheSecretCircle Faye Chamberlain]]?
** [[Series/OneTreeHill Lucas's girlfriend Lindsay]] is a werewolf.
** Creator/GinaTorres is Bree.
** Bonnie's human father was a [[Series/{{Supernatural}} vampire on another show]].
** [[SeventhHeaven Simon Camden]] is Ray.
** [[Series/TheOC Julie Cooper]] is Matt and Vicki's mom.
** April used to be friends with [[TheNineLivesOfChloeKing Chloe King]].
** [[Series/{{Arrow}} Green Arrow]] is Brady.
** [[Film/LegallyBlonde Warner Huntington III]] is Alaric.
** [[WizardsOfWaverlyPlace Stevie Nichols]] is Megan
*** She's also [[LemonadeMouth Stella]] and Ray is Luke.
** In a humorous example Nina Dobrev and Dillon Casey (who played Noah), both once played the romantic leads in a LifetimeMovieOfTheWeek
** [[TheLeague Shiva Kamini Soma Kandarkram!]]... is Qetsiyah.
** Aaron used to be [[LifeUnexpected Lux's teacher]]
** Damon and Series/{{Dexter}} have the same dad...that makes perfect sense.
** Kai used to sleep with [[TheCarrieDiaries Carrie Bradshaw]] when she was in high school.
** One of Lily's heretics is [[Franchise/HarryPotter Pansy Parkinson]].
* HeyItsThatVoice: Jason Spisak ([[VideoGame/FalloutNewVegas Vulpes Inculta]], [[WesternAnimation/YoungJustice Kid Flash]], [[WesternAnimation/GreenLanternTheAnimatedSeries Razer]]) provides the voice of Silas.
* IKnewIt: Show of hands: how many of you called [[spoiler: Stefan having killed his father?]] [[TheUntwist Yeah, thought so...]]
** Also in "The Departed" who guessed [[spoiler: the only way to kill Alaric would be to kill Elena and turn her into a vampire.]]
** Is there anyone who actually thought [[spoiler: Jeremy was going to come out of the hunter storyline alive?]]
** Many people guessed the third sacrifice would have consist of twelves witches.
** Also many people predicted Silas's lover would like [[spoiler: Elena]]
* McLeaned: [[spoiler:Alaric]] was killed shortly before it was announced that CW would pick up a new show starring his actor.
* RomanceOnTheSet:
** Ian Somerhalder and Nina Dobrev.
** Candice Accola and Steven Mcqueen also dated but their characters were never really involved with each other.
** Paul Wesley's wife Torrey Devitto plays Meredith Fell.
* WhatCouldHaveBeen:
** Originally, the 4th-season-spanning [[spoiler: cure]] storyline was supposed to resolve with [[spoiler: Damon being the one to receive the cure]]. However, almost immediately after introducing [[spoiler: the cure]] as an idea, the writers were dismayed to find that a large number of fans were predicting that very outcome. So they changed mid-course, and [[spoiler: the cure was instead given to Katherine.]]
** A deleted scene reveals Kelly Donovan, Matt's mother, as a succubus.

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