Linda Cardellini, 'Mad Men' superfan, on her Emmy nom

Mad Men is a series that traffics in secrets, both onscreen (Don Draper’s increasingly less obscured past) and behind the scenes (creator Matt Weiner’s famous reluctance to reveal any information about what’s coming next). But though the show’s sixth season featured plenty of unanticipated shocks, its two biggest both involved one top-secret new character: Linda Cardellini’s Sylvia Rosen, a bored housewife who a) had an affair with Jon Hamm’s Don (gasp!) which led to b) Sally Draper (Kiernan Shipka) discovering her father cheating on his wife (double gasp!!).

It was an undeniably juicy guest role — which is why the Emmy Awards honored Cardellini with her very first nomination this morning. The actress, best known previously for her work on Freaks and Geeks, is understandably over the moon: “It feels amazing!” she gushed to EW today. “When I started the part, I didn’t know what it was I would be doing. And so having it unfold the way it did was amazing. And the idea that she is sort of a catalyst for all these things that happen in Don’s life — it became such a great role. So that happening, and now this on top of all that, it’s really a dream.”

The nod seems doubly rewarding for Cardellini, considering how hard she had to work to keep her role under wraps. Weiner had the actress travel to the set in a van with covered windows; she wasn’t allowed to attend the show’s premiere party, since that would reveal her involvement with the show. Cardellini claims that keeping quiet was “really fun” — but she also seems relieved that her days of subterfuge are over. “Now I get to go to things!” she enthused. “That’s such a great thing about the secret being out: I can actually go to the parties with everybody.”

Then again, Weiner does seem to have rubbed off on Cardellini since she wrapped her role. After Sally caught Don and Sylvia in the act, Cardellini’s character disappeared; viewers don’t know how she handled the aftermath of that horrible moment. Which is fine with Cardellini: “I’m a fan. I want to see the way Don deals with it,” she explained.

In fact, she’s such a fan that when Weiner invited her to attend the table reads for season 6’s last two episodes — in which Sylvia does not appear — Cardellini turned him down. “I told him that I couldn’t come, because I wanted to be surprised,” she said. “I love the show, and I figure, I kept the secret so long about my character — I might as well have it be secret to me, what happens. So the end of the show was a total surprise to me.”

Cardellini’s plan worked — and she, like the rest of Mad Men‘s fans, was floored by where Don ended up in the season finale (quasi-fired, quasi-separated, revealing to his kids and colleagues that he grew up in a dilapidated whorehouse). Cardellini’s love for Mad Men may be second only to her love for her frequent scene partner Hamm. “Everybody on the show is so talented — but I think Don Draper is such an iconic character, and an iconic television presence, and I don’t know that there’s anybody that could play it like he does,” she told EW. “I don’t think there’s anybody [else] in the world that could play that part.”

And that’s no secret.