It’s hard to know what to say when someone suddenly gains 50 pounds, especially when that someone isn’t a pregnant woman.

Rob McElhenney, star of FX’s “It’s Always Sunny in Philadelphia,” is thriving on the awkwardness he created by increasing his body mass by nearly a third – just because he thought it would be funny.

Fortunately, Nick Kroll of FX’s “The League” has no filter. We were on hand recently as Kroll talked to McElhenney about his weight gain — and left no question unturned.

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Before we get into it, a little background:

“Sunny” tears down sitcom conventions and aspires to make its characters as unlikable as possible. McElhenney noticed that characters always get better looking in later seasons, as storylines get more syrupy and their stars get richer.

As his show entered its seventh season, he decided sudden weight gain would be a perfect way to mock other shows and capsize the relentless vanity of his character, Mac. (He tried to get the whole cast to join in the weight gain, but all passed. His wife, Kaitlin Olson, was especially uninterested after having their first child last year.)

McElhenney has already lost nearly half the weight in a month, after spending five months packing it on. As he spoke with TheWrap and Kroll, McElhenney ate a sensible lunch of pasta and salad (pictured at right). In case you were wondering.

Warning: The following discussion of every aspect of sudden weight gain gets very graphic.

To gain the weight, you ate five 1,000-calorie meals a day. What were they?

ROB MCELHENNEY: As I started off I was doing it with chicken breast and rice and vegetables. But when you’re four months in it and you have to muscle down 1,000 calories for the third time or fourth time in a day and you have to either eat three chicken breasts, two cups of rice and two cups of vegetables — or one Big Mac — you start to see the Big Mac and realize it’s a lot easier to get down … And then every once in a while I would eat three donuts. And every day one of my meals was a high-calorie protein shake.

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NICK KROLL: You look good. It’s coming off. Do you miss it?

MCELHENNEY: I do. I never felt lethargic. I felt great. I felt f—ing great.

KROLL: You felt like an American.

MCELHENNEY: And I feel like for the first time in my life I’ve been watching the show like, “All right, I’m almost as funny as everybody else.”

Was it a fat-men-are-jolly kind of thing?

MCELHENNEY: Yeah, I was jolly as f—. And I was just full of energy, because I was eating so much. It was just constant fuel.

KROLL: Now, did you get fat man’s dick?

MCELHENNEY: Well, first of all, I don’t exactly know what you mean by that, but I will say this: My legs and my gut got so big that my penis looked even smaller.

KROLL: Yeah, that’s what I’m saying. Fat guy’s dick.

MCELHENNEY: It’s insane. It really is a very, very crushing psychological gain.

KROLL: Did it look like a penny with a button on the end?

MCELHENNEY: A friend of mine recently described his penis as a button on a fur coat. So we put that in the show this year.

When I first heard about this, I assumed you just gained a lot of sympathy weight during your wife’s pregnancy and decided to pretend it was for the show.

KROLL (at left): Uh-huh.

MCELHENNEY: I’m so happy that people might think that.

Do you think you could get an Emmy for committing like this?

MCELHENNEY: I’m going to go on the record saying there is no f—ing way in hell that anybody – well, maybe Charlie [Day], at one point might, if he becomes a big enough movie star – might actually get nominated for an Emmy.

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When did you decide to stop gaining and turn it around?

MCELHENNEY: The end of [shooting] the show. I started at 160 and I got up to 212. And I thought, that’s enough.

And you’ve lost 23 pounds in a month? That’s the most amazing part of this.

MCELHENNEY: Losing it is easy. You just stop eating so f—ing much. [I’m also] working out three times a week. Regardless of your metabolism, if you stop consuming so many calories, you will lose weight.

KROLL: No, not everybody. I mean some people -

MCELHENNEY: I’m not saying it’s not difficult. It’s definitely more difficult depending on your genetic makeup. But it’s just true that if you decrease the amount of calories you are eating you’re body doesn’t have the fuel to create fat.

KROLL: Did your body get used to -

MCELHENNEY: Oh, I got way used to it. It was f—ing awesome.

KROLL: Were you s—ing like a maniac?

MCELHENNEY: Um, you know, it wasn’t more volume -

KROLL: Was it looser?

MCELHENNEY: It was almost exactly the same. And consistent. Still at the same time every day.

KROLL: That’s great. Good for you.

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It sounds like you’re really lucky. Most people would have a harder time losing it.

MCELHENNEY: I was really fortunate. I’m lucky I have the metabolism. It was really fun. You know what the most fun was, was getting rid of any shred of vanity.

KROLL: Well you were talking about the theory that everybody gets better looking on TV as shows go on. And since you said that I thought about it … everybody gets trimmer, and, you know.

MCELHENNEY: Even the nerds on “Big Bang Theory” are getting better looking. Their clothes are getting nicer. They’re better groomed. It works for them. But this show – it’s not like that.

KROLL: You’re the f—ing Daniel Day-Lewis of basic cable.

MCELHENNEY: I want to be part of that conversation. I want to be part of the DeNiros, the Bales, the Day-Lewises.

KROLL: You’ve got to do “The Machinist” next year.

The seventh season of “It’s Always Sunny in Philadelphia” premieres Sept. 15. “The League” returns for its third season Oct. 6.