Revealing mistake: As Mac says "I'm very worried about these guys" and exits the bar, there's a shot right through the door and it's not the bar inside at all, just a wall with some pictures on it, much closer to the door than it should be.
It's Always Sunny in Philadelphia (2005)
1 revealing mistake in season 13 - chronological order
Starring: Danny DeVito, Charlie Day, Glenn Howerton, Kaitlin Olson, Rob McElhenney
Genres: Comedy
Other mistake: In the opening of this episode the screen reads "3:50pm On a Wednesday." When Gino (Frank's Brother) is reading the letters meant for Shadynasty, he says "Meet me at the airport, Friday, at 5:00, Terminal C." The gang and Gina then go along to the airport that very afternoon - a Wednesday - to try and meet Shadynasty and get her and Frank back together. And of course she is there, despite it being a Wednesday, not a Friday.
The Gang Gets Held Hostage - S3-E4
Trivia: When Frank pulls out the gun on the roof, he says "Yippee-ki-yay Mr. Falcon", a nod to Die Hard 2, the TV version of which infamously had the word "motherfucker" badly dubbed over with "Mr. Falcon."
Bums: Making a Mess All Over the City - S3-E14
Question: Does the junkyard cat actually belong to one of the actors or is that a whole different deal?