Stefan Salvatore (Paul Wesley): Season 1 vs. Season 6
In Season 1, Stefan was doing ANYTHING and everything to impress Elena Gilbert. Since then we've seen him lose Elena and his humanity (but eventually he regained the humanity bit). Plus, he's also ~kind of~ having a thing with Caroline.
Elena Gilbert (Nina Dobrev): Season 1 vs. Season 6
Oh, how far Elena has come! From a young girl trying to find herself and dealing with the fact that her beau was a vampire to becoming a full-on vamp in Season 3 in the episode "The Departed." She managed to avoid turning for so long, but now that she's here she's making the most of it, and studying to become a doctor (because she has eternity...right?).
Damon Salvatore (Ian Somerhalder): Season 1 vs. Season 6
When we first met Damon he was the eternal bad boy — kinda mean, but in a way that you also crushed hard on him. He's always had ~something~ with Elena, and now that we're in Season 6, they're actually a real item.
Matt Donovan (Zach Roerig): Season 1 vs. Season 6
In the pilot episode, we learn that Elena broke Matt's heart when she ended their relationship. Despite that, Matt and Elena remain besties for much of the series. That is, until Matt is killed and brought back to life over and over again. It's gotten to a point where now, in Season 6, episode "I Could Never Love Like That," he tells Elena he hates vampires and refuses to take her blood to heal his wounds.
Oh, and he's a cop in training, or something.
Jeremy Gilbert (Steven R. McQueen): Season 1 vs. Season 6
Jeremy has had QUITE the transformation from the loner, stoner kid we met in Season 1 to the vampire hunter he is now. Like so many others in Mystic Falls, he's been killed, brought back to life, and killed again a few times. At one point, he started to see the ghosts of his dead girlfriends, then he discovered his knack for hunting vamps... As of now, he's "living in Santa Fe" in an attempt to move on.
Tyler Lockwood (Michael Trevino): Season 1 versus Season 6
Tyler was kind of a dick in Season 1 — THERE, I said it! But for good reason: He was figuring out that pesky werewolf gene. Now in Season 6, his werewolf instincts are on the back burner, and he's also a cop-in-training, like Matt. He also had a long and dramatic relationship with Caroline throughout the series, but that's now also over. [insert sad emoticon]
Caroline Forbes (Candice Accola): Season 1 vs. Season 6
In Season 1, Caroline is almost immediately turned into Damon's plaything and forced to wear all manner of scarves to hide her love bites. But by the beginning of Season 2, she's a vampire herself. Now, in Season 6's episode “Let Her Go," she's decided to turn off her humanity switch, which has made for some very un-Caroline moments, like killing random strangers, for example!
Bonnie Bennett (Kat Graham): Season 1 vs. Season 6
Bonnie started off the series as a newbie witch, getting her bearings after Grams told her the truth about her special powers. Since then, poor Bonnie has seen some shit: She's died, appeared as a ghost to Jeremy, come back to life, had to bring Jeremy back to life, and the list of horrors goes on. Including most recently, when she was stuck in a prison world with a witch named Kai who essentially tortured her. Poor Bonnie. BUT! She cut off most of her hair into a fierce bob, so there's that.
Alaric Saltzman (Matthew Davis): Season 1 vs. Season 6
Alaric came in in Season 1, just looking to find some closure regarding the disappearance of his wife, only to discover that she willingly became a vampire and left him. Then Alaric himself became a vampire, then a ghost, and has now been brought back from the dead. TL;DR: Alaric is alive and well, with a baby on the way and teaching some college courses.
Elena and Bonnie
Do you remember the pilot of The Vampire Diaries? Bonnie is boy-crazy. And a witch. It's fantastic! She also doesn't trust Stefan one bit when it comes to his intentions with Elena.
Cut to now, and Bonnie and Elena are still besties. Bonnie remains wary of vamps, but she's definitely learned to live with them.
Stefan and Damon
In the first season, these brothers are at major odds: Stefan is trying to turn over a new leaf, and Damon is having a hard time forgetting the past.
Now they're definitely more on each other's side and have stopped fighting over that whole "WHO GETS ELENA?!" business...for now.
Elena and Damon
Come on, there was always sexual tension between these two. Even when Elena was dating Stefan, and even when she tried to convince herself to steer clear of Damon...
Now in Season 6, they're head-over-heels, and it's super-cute. They also take showers together, which is less cute and more sexy.
Elena and Stefan
This couple was everything in Season 1 — Stefan was charming in that "I happen to know everything, including the dates of every historical event ever" way, and Elena was finally letting herself open up to someone. It was sweet, and their first kiss was epic.
Now in Season 6, they've split up, but they're still extremely close and tend to work together a lot as equals. (Remember when they needed to work together to try to get Caroline's humanity back?) #stelena4ever
Caroline and Elena
Caroline is almost always the bright and bubbly ray of sunshine in all of her friends' lives. And she was that for Elena in Season 1 — always game for fun, and ready with a witty quip.
This season, she's been a little...out of sorts — what with losing her humanity and everything. But she's still got that sense of humor, even if it's a dark sense of humor now.
Caroline and Stefan
They've always been super-great friends, so as it goes with friendships in Mystic Falls, this was bound to turn into something else. Now that Caroline and Stefan have slept together — albeit in altered states — who knows what's going to happen with these two.
The Vampire Diaries cast may seriously be vampires IRL, though.
THEY NEVER AGE.