Exclusive: 'Always Sunny' has a very funny blooper reel

How do the stars of FXX show It's Always Sunny in Philadelphia keep a straight face? 

Well, they don't.

Exclusive: 'Always Sunny in Philadelphia' gag reel

This blooper reel shows that Danny DeVito and the gang sometimes break character when things are too funny. Season 11 of 'Always Sunny' airs Jan. 6.

In an exclusive blooper reel, see Dennis, Dee, Charlie, Mac and Frank (Glenn Howerton, Kaitlin Olson, Charlie Day, Rob McElhenney and Danny DeVito) totally break after their costar says something ridiculous.

Always Sunny's Season 10 DVD is available Jan. 5, with an extended version of the gag reel. Season 11 of the comedy airs Jan. 6.