It’s Always Sunny In Philadelphia is coming up to its fourteenth season, and despite having some of the least likeable characters on television, it's only gone from strength to strength.

Unlike a lot of shows that run this long, Sunny has only had a couple of big name celebrities over the years, and it’s typically stayed away from ratings bait guest spots.

Sure, three of the four Kings Of Leon appeared at the high school reunion, but there was no special celebrity spotlight; two played bartenders and the other a customer angry at Mac.

With stellar writing though, what it hasn’t been short of is magnificent one-off appearances from brilliant characters. While they haven't often called in huge names to pique interest, there's still been some fantastic guest spots littering the show's stellar run. Many series that last this long start trading on celebrity names, but It's Always Sunny has largely gone for substance over style.

Some of these mesh with the Gang perfectly, while others clash against them in the best way.

With show as unique as It’s Always Sunny, there was of course plenty of bizarre characters to choose from, but it’s strictly one episode only, so the likes of Schmitty, Maniac and not-Bruce Mathis all just miss out.