The gang’s going to be all back together for the majority of It’s Always Sunny in Philadelphia: Season 13. Stars/producers Rob McElhenney and Charlie Day confirmed that Glenn Howerton’s character will return for “pretty much every episode” in the forthcoming season on FXX.
“He’s in pretty much every episode,” said McElhenney, with Day adding, “He’s in the majority of them, and then we have a couple … that focus more specifically on other characters.”
“Everything just worked out from a schedule standpoint,” Day later added to IGN of Howerton’s return. “Dennis — or some form of Dennis —
can see in the show a lot. The type of Dennis that they see — and I can’t always guarantee that it will be the actor — but the spirit of Dennis will be there.”
Source: IGN.com Dennis to Appear in 'Pretty Much Every' It's Always Sunny: Season 13 Episode