'I was trying to destroy myself physically,' McElhenney says of gaining 50 pounds to play Fat Mac, one of MTV News' Top 50 TV Characters of 2011.

Gregor Samsa became an insect. Hulk Hogan dyed his beard black and joined the nWo. Metallica used to be awesome.

Transformations are as much a part of life as eating, breathing and making fun of Lulu, yet rarely are they as unexpected as the grand, grotesque metamorphosis Rob McElhenney pulled off on the seventh season of "It's Always Sunny in Philadelphia," when he turned the formerly fitness-obsessed Mac into a bulbous, bloated buffoon ...

mostly because he thought it would be funny.

But McElhenney was also making a deeper point, too. By gaining 50 pounds of solid fat, he took a not-too-subtle jab at one of TV's oldest tropes: Namely, that as shows go on, characters don't age and they seemingly get better-looking. It's the kind of deconstructionist slant that has made "Sunny" a cult favorite and made Fat Mac one of the year's best characters. Because while, sure, it was funny to watch him inject insulin into his ginormous gut, you couldn't help but ask yourself why there aren't more characters like him on network shows.

So, in celebration of Fat Mac's inclusion in MTV News' Top 50 TV Characters of 2011, we spoke to McElhenney about piling on the pounds, the silky comfort of Tommy Bahama shirts, and how, someday, he hopes to be considered "the De Niro of basic-cable comedy."

MTV News: First off, congratulations on making our list of the Top 50 TV Characters of 2011. Fat Mac actually came in at #8 on the list.

Rob McElhenney: I made the top 10? F--- yeah! That's really awesome. Who was ahead of me? [We start reading McElhenney the list, but he makes us stop when we reveal that Snooki came in at #3.] What?

Are you f---ing kidding me? I refuse to hear anything else. Jesus Christ.

MTV: Mac's transformation was one of the television highlights of the year, and not just because it's funny to see him, you know, lug around a garbage bag filled with chimichangas. You just don't see characters put on that kind of weight on sitcoms now, or really ever before.

McElhenney: Yeah. Vanity is such a huge part of television, and if you watch any average sitcom, you notice that the actors get better-looking as the years go by. And I caught myself sitting in the editing room last year, looking at myself, and I said, "Man, I don't look very good in this scene; I should try to find a different shirt or something next time." And I realized, "Wow, that is the first time I'd ever really thought that." So I realized I needed to go in the extreme opposite direction. It's always been our goal to do the opposite of what any sitcom on network television would do, so that's what I did.

MTV: So it went beyond, just, "It would be funny to see Mac gain an obscene amount of weight ..."

McElhenney: It wasn't just a stunt. I thought, if we were being true to the characters, and we were really showing what these people would look like if they lived the way that they claimed to live, this is what we would look like. All we do is sit around and drink and eat terrible food, and there's certainly no exercise going on, and we don't seem to really care about our health. So when you hit a certain early-30s, mid-30s range, it's going to start to fall apart.

So, to me, it was less of a stunt or a gag and more of an actual representation of what Mac really might look like at this point in his life.

MTV: So once you decided you were going to gain the weight, how'd you go about doing it without, you know, totally destroying your body?

McElhenney: Oh, I was basically trying to destroy myself physically as much as I possibly could. I was trying to eat around

5,000 calories a day, and at first I was doing it as healthy as possible, but after like the 3,000th calorie of grilled chicken breast and rice, you realize you literally have to consume twice as much volume as opposed to just eating a cheeseburger. So after a while, I started eating a lot, a lot of doughnuts. It was really hard, man. The key to it was force-feeding myself this milkshake that I made every day that had weight gainer, chocolate milk, chocolate ice cream, and creatine, which creates bloating, and force-feeding myself two of those every day, and those were about 1,000 calories a piece, and that's what really put it over the edge.

MTV: You know, it's funny, because you hear about all these actors gaining or losing weight for roles, and they're almost always lauded for doing so. Does it bother you that, after going through so much, people only see Fat Mac as this sort of stunt?

McElhenney: Well, I'd like to enter that conversation. You know, "the De Niro of basic-cable comedy." [He laughs.] Nah, it doesn't bother me. We're not that kind of show. But I don't think people understand how hard it was to just gain all this weight. I started at 162 and I got up to 212 ... and I was also working out, just doing, like, powerlifting, because I noticed that most of my weight was just going to my gut, and it wasn't filling out everywhere else and it wasn't really playing, so to create that sort of non-defined, smooth look, I had to lift weights, and then the fat just sort of sat on top of the muscle. I was trying to create David, and as we all know, Michelangelo had to start with a slab of marble and then whittle it down. So I was just creating the slab.

MTV: Another great thing about the character this season is that he introduced the Tommy Bahama shirt into the national conversation.

McElhenney: [He laughs.] I see a lot of people wearing them. And I think middle-aged guys wear them because they think it hides their gut, and it doesn't. In a bizarre way, it makes them look bigger, and originally I was wearing these super-tight T-shirts, and since my fat was kind of rolling out from underneath it, you would think that you would look bigger onscreen that way, as opposed to this big, flowing shirt. But for whatever reason, they actually accentuate the size. They're like a muumuu. And the truth is, once you slip one of those bad boys on, they're unbelievably comfortable. They're made out of silk, and they really just flow and they breathe, and I was like, "Goddamn, I kind of really love these shirts." I took some home, but my wife ["Sunny" co-star Kaitlin Olson] wasn't having it.

MTV: One of the key episodes this season was "How Mac Got Fat,"

which, as the title implies, explained why he put on all the weight.

There are scenes of you in flashback when you were skinny. Can you explain the backstory of that episode?

McElhenney: We shot it last season, and it was a completely different episode and we were going to air it this year, because we had one less slot last year. So that was always the intention, and then as we started the season, and I went through this endeavor, we realized we couldn't just air this episode because it wouldn't make sense anymore.

So we sort of broke down the episode and said, "How can we tell this as a flashback, and create this as being the reason why Mac did this in the first place?" So we rewrote it, based on the cut and based on the footage we had, and then we went back and created this completely different episode. It was literally the last thing we shot this season.

MTV: So, finally, we know you've dropped most of the Fat Mac weight now. Looking back, how do you feel about the entire endeavor?

McElhenney: Yeah, I've dropped almost all of it. I think the remaining 10 to 12 pounds are probably just going to stay. I'm OK with that. [He laughs.] And, you know, I'm really happy I did it. It was hard, but it was worth it. I can tell you right now that this never would've happened on network television. Because when I would've gone in to pitch it to the network executives, they would've said, "Absolutely not." Because the glamour is such an important part of how they sell their shows, so trying to make the actors look as good as they possibly can is an important part of the process. And our show has never been about that.

MTV will reveal the best artists, songs and movies of the year. Come to MTV News each day to see more big reveals and check out more of MTV's Best of 2011 music, TV, movies and news coverage.