The secret was finally revealed in what turned out to be a rather lackluster episode of 'It's Always Sunny in Philadelphia' (Thu., 10PM ET on FX). Considering what a big deal was made of Rob McElhenney gaining all that weight for this season, it hasn't borne the comedic fruits it seemed he intended.

And now, with the episode that finally revealed why he gained all that weight in the first place, it turned out to be somewhat disappointing. The most intriguing thing about the episode was that Charlie was the voice of reason and sanity when everyone else was letting the bar's success go to their heads.

But the actual explanation was completely ridiculous. Mac was gaining weight to match the weight of his muscle-bound avatar, only that scheme had been abandoned so long ago the others barely remembered it. We never did find out why the bar suddenly became successful, though.