It's Always Sunny In Philadelphia's Mac definitely has some issues with his body. He's always talking about the 'mass' he's putting on or gushing about his gym workouts, despite other characters letting him know he only really works out his "glamour muscles". However, the character went through some dramatic changes for the series' seventh season.

Out of nowhere, the first episode of this season showed Mac having gained a considerable amount of weight. It wasn't until the tenth episode of this season that we found out why the character chose to do this (it was a scheme far too convoluted to describe here), but Rob McElhenney did reveal why he chose to put on the pounds for the character behind the scenes.

That's right - there was no fakery with this transformation.

McElhenney, who also created the show and acts as one of its writers and executive producers, effectively did the whole thing as a joke. Knowing that it was in character for Mac to wildly misunderstand things and obsess over his own image, he packed on weight over an incredibly short amount of time.

Mac's complex vanity led him to see the weight gain as developing muscle ("cultivating mass" in his words) to go from "a tiny twink to [a] muscle-bound freak". For McElhenney, it was also an opportunity to poke fun at other sitcoms, in which relatable characters become more well-groomed and conventionally attractive as the seasons pass.

Speaking to The Wrap about how he gained so much weight, he said:

"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." 

However, he's now bounced back - going from 'Fat Mac' to insanely-ripped Mac. He was spotted, in what is admittedly one of the best photos ever, at the Philadelphia Pride parade alongside co-star Danny DeVito.

Seeing the 73-year-old DeVito dressed up and celebrating the LGBTQ community is such a powerful and all-round brilliant thing that it's easy to miss that it's McElhenney stood behind him.

Fans simply couldn't believe it.

Then another image surfaced, this time showing McElhenney with his wife and It's Always Sunny co-star, Kaitlin Olson.

He even popped up on the Instagram of LA Dodgers second-baseman Chase Utley, who was pretty impressed.

And honestly, aren't you?

Just look at the massive changes he's made:

Either way, it looks like not only is 'Fat Mac' a thing of the past, but the next season of the hit comedy will be bringing on one who practically looks superhuman.

It's Always Sunny In Philadelphia's Mac definitely has some issues with his body. He's always talking about the 'mass' he's putting on or gushing about his gym workouts, despite other characters letting him know he only really works out his "glamour muscles". However, the character went through some dramatic changes for the series' seventh season.

Out of nowhere, the first episode of this season showed Mac having gained a considerable amount of weight. It wasn't until the tenth episode of this season that we found out why the character chose to do this (it was a scheme far too convoluted to describe here), but Rob McElhenney did reveal why he chose to put on the pounds for the character behind the scenes.

That's right - there was no fakery with this transformation.

McElhenney, who also created the show and acts as one of its writers and executive producers, effectively did the whole thing as a joke. Knowing that it was in character for Mac to wildly misunderstand things and obsess over his own image, he packed on weight over an incredibly short amount of time.

Mac's complex vanity led him to see the weight gain as developing muscle ("cultivating mass" in his words) to go from "a tiny twink to [a] muscle-bound freak". For McElhenney, it was also an opportunity to poke fun at other sitcoms, in which relatable characters become more well-groomed and conventionally attractive as the seasons pass.

Speaking to The Wrap about how he gained so much weight, he said:

"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." 

However, he's now bounced back - going from 'Fat Mac' to insanely-ripped Mac. He was spotted, in what is admittedly one of the best photos ever, at the Philadelphia Pride parade alongside co-star Danny DeVito.

Seeing the 73-year-old DeVito dressed up and celebrating the LGBTQ community is such a powerful and all-round brilliant thing that it's easy to miss that it's McElhenney stood behind him.

Fans simply couldn't believe it.

Then another image surfaced, this time showing McElhenney with his wife and It's Always Sunny co-star, Kaitlin Olson.

He even popped up on the Instagram of LA Dodgers second-baseman Chase Utley, who was pretty impressed.

And honestly, aren't you?

Just look at the massive changes he's made:

Either way, it looks like not only is 'Fat Mac' a thing of the past, but the next season of the hit comedy will be bringing on one who practically looks superhuman.