Basically, that one acting credit or appearance by someone that completely turned you around on that actor/actress or made you a fan. I was rewatching Criminal Minds, Season 4 episode 16, and I always get blown away by Brianna Brown's performance as a serial-killing call-girl. There's just so much emotion and depth in the entire episode that it's basically my favorite episode ever of Criminal Minds and maybe of any tv show.

So, have at it. What appearance by which actor/actress on what tv show/movie/whatever made you a fan?

 

There's episode of Dollhouse where Enver Gjokaj (Victor) is implanted with the personality of Topher. I'd already been hugely impressed with the revelation that his first few appearances had been false, but he absolutely nailed the speech and mannerisms of another main character. It really was like having both of them on screen at the same time, and it's probably one of the best pieces of acting I've ever seen.
Theoretically, the whole show ought to have been this, given the basic premise, but they didn't really manage it tbh. Although I guess you could count Alan Tudyk as well. His role didn't sell me on him as an actor - Firefly and, to a certain extent, A Knight's Tale had already done that - but it showed he wasn't just a loveably comic type.

When Matt Smith was first announced as the Eleventh Doctor, I was dubious. He looked too young, the outfit looked ridiculous, the only thing I'd seen him in had been absolutely dreadful...then there was the regeneration in The End of Time, which was kind of ok, but didn't really grab me. By the end of his first full episode, I was completely sold, and hadn't been as excited about the show since The Christmas Invasion a few years previously. He's still the best thing about the show, and I think some of the lesser episodes get by more on good will from his performance than the scripts etc.

On a semi-related note, David Tennant as Hamlet with the RSC. Absolutely incredible.

 

Well, I'm going to go against all logical and not say Heath Ledger as the Joker. Instead, I'm going to say Nathan Fillion from Firefly. Sure, his character may or may not have been overshadowed by the awesomeness of Jayne, but it was still memorable enough for the actor to be the sole reason for me to pick up Castle, and enjoy the fuck out of it as well.

 

Can we do this the other way around as well?

Because my esteem for Clint Eastwood took a nosedive recently.

 

Really? I thought he did wonders for Obama's campaign in recent times.

 

Mark Sheppard in Firefly 1x01, Serenity. Immediate fan. This sort-of-applies to all the main actors of the show as well. I don't think anything will ever come close to the magic surrounding that series. Incredible.

Ellen Page in Juno. Immediate fan.

Michelle Williams in lots of stuff after glimpses of Dawson's Creek. She won me over.

Jay Baruchel in Million Dollar Baby after a so-so performance in Undeclared. He won me over.

 

I remember being pretty impressed with him in that episode, too.

Of course, I always had my Friday pizza while I was watching that show, which is guaranteed to automatically increase my goodwill toward what I'm watching.

He played another creepy guy in an episode of C.S.I..

 

Scott Adkins in Undisputed 2 & 3 as Yuri Boyka, aka the Russian god of war. I'd never seen him in anything before Undisputed 2, but my god did he knock the ball out of the park with Yuri Boyka. As far as I'm concerned, he should play that character in every movie ever.

 

Leonardo Decaprio in Inception. I had seen him in plenty of other movies but his acting in them had always annoyed me more than anything. Like The Departed, great film with phenomenal acting but Leo never clicked for me. He had some good scenes but when half of your screen time is overshadowed by Markie Mark then you're doing something wrong. For Inception he knocked it out of the park for me.

 

I agree about the call girl episode, was a really good one.

Richard Armitage who plays John Porter in Strike Back, I found him a brilliant actor.

David Dayan Fisher who played Trent Kort on NCIS, easily my favorite character on the show.

Enrico Colantoni on Person of INterest, amazing, absolutely amazing, I watched his other show Flashpoint when I saw he was in it.

 

Brad Pitt in Seven and then in Fight Club, because I watched both of them about the some time. Before I just though of him as another pretty face.

Natalie Portman in Léon: The Professional. I actually saw it few years after it was released, but because I didn't see any other film with her nor hear about her before (wasn't really interested in movies back then), I can say that I was her fan every since her debut on the big screen.

This movie also made me like Jean Reno and Gary Oldman, though it was Dracula that made me a real fan of the second one.

Chloe Moretz in Kick Ass. She is already on of the best child actors in the history in my opinion. Time will tell if she will also become one of the greatest adult actors like Portman did.

He will always be first and foremost Keith Mars to me.

 

Mark Pelligrino in Supernatural. He pretty much made the whole Lucifer-Apocalypse season of Supernatural for me. The guy was just so good at being creepy as fuck.

Michael Fassbender in X-Men: First Class. A good representation of what I always thought Magneto was like when he was young.

 

Mark Addy in Game of Thrones. A near perfect King Robert Baratheon from someone I had seen entirely as a comic actor.

 

Daniel Craig in Munich. I'd seen him before in Road to Perdition, but Munich was where I realized how talented he is. Go watch both of those movies if you haven't yet done so.

Paul Giamatti in American Splendor, though he didn't quite steal the show. He was also incredible in The Illusionist and John Adams.

Russell Crowe in A Beautiful Mind. Yes, he was also very good in The Insider, Gladiator, and L.A. Confidential previously, but ABM was the role for which he *should* have won the Oscar.

Philip Seymour Hoffman in The Talented Mr. Ripley. 'Nuff said. Same for Joaquin Phoenix in Walk the Line.

Kate Winslet in the Kenneth Branaugh rendition of Hamlet. Dayum. And she's been riveting in every role ever since. I've had a crush on her for years and years now.

Liam Neeson in Schindler's List. It's even more amazing when you realize he was in Next of Kin with Patrick Swayze just four years earlier. ... Yeah.

Benicio Del Toro in Traffic. He was also great in The Way of the Gun but I first saw him in Traffic.

Ed Norton in practically anything, but that's not the point of the thread. I realized his talent as early as Primal Fear but it really shines in American History X. The movie is a little preachy or maybe pandering or... something, but Norton is incredible in it nonetheless.

Jake Gyllenhall in Donnie Darko. The movie is a mind fuck whether you liked it or didn't, and JG was my favorite part other than that creepy fucking rabbit.

And for those DiCaprio fans saying his work in Inception changed your opinion, kindly go jump off a cliff. But first, go and rent or pull up on Netflix the movie What's Eating Gilbert Grape. If that movie doesn't convince you of DiCaprio's talent then nothing ever will.

 

Joel McHale, now of "Community" fame as Jeff Winger. He had a cameo role in Spiderman as a banker or something, and I just always remembered him as being a hilarious narcissist, even though he was only on screen for about a minute. The fact that he now plays almost exactly the same role in Community to such great effect just shows that he really got the character out there in a really short amount of time.