Summary

• Always Sunny in Philadelphia continues to delight fans with guest appearances that add to the show's success.
• Actors like Retta, Brian Huskey, and David Huddleston bring extra charm to the series with their roles.
• Guest stars like Dolph Lundgren and Judy Greer add a fresh twist to episodes and leave a lasting impression.

It’s Always Sunny in Philadelphia has been on television for almost two decades, and while the lead characters running Paddy's Pub are the series' biggest appeal, several It's Always Sunny guest stars have stolen the show. Surprisingly, It's Always Sunny in Philadelphia's formula hasn't gotten old, as the show has rarely strayed from what made it successful, which is the so-called best friends and co-owners of Paddy's Pub constantly stabbing each other in the back for personal gain.

However, while It's Always Sunny in Philadelphia has an incredible main cast, including Glenn Howerton (Dennis), Charlie Day (Charlie), Rob McElhenney (Mac), and Danny DeVito (Frank), It's Always Sunny guest stars have become some of the most lovable characters. The Gang has often played second fiddle to some big-name actors. Some guest stars have reprized their roles multiple times because their characters are that good, but other guest appearances left fans feeling they could’ve done without them.

22 Retta As Hardware Store Clerk

“The Gang Gets Extreme: Home Makeover Edition”

Retta is best known for her role as Donna Meagle in Parks and Recreation — the girl knows how to treat herself, as evidenced by her famous meme. But her appearance in It’s Always Sunny was so small that it's easy to miss. In season 4, episode 12, “The Gang Gets Extreme: Home Makeover Edition,” Charlie and Dennis go shopping after kidnapping the Juarez family, and they are now forcefully renovating their house. This means they need supplies and head to the hardware store.

Retta plays the clerk at the hardware store where the gang is picking up the supplies. Like many other guest stars, Retta plays it straight and has to listen to Charlie's ludicrous ideas. The guest star is fun for fans of Parks and Recreation, but she doesn't have much material to work with. She doesn't get the chance to say much, but her facial expressions are brilliant in response to Charlie's comments. Retta also stars in the TV show Good Girls and has a role in the movie Good Boys.

21 Brian Huskey As Gary

"2020: A Year in Review"

Brian Huskey features in season 15, episode 1 of It's Always Sunny in Philadelphia, "2020: A Year in Review." The episode has one of the most unique concepts in the series, as it takes advantage of all the catastrophic events in 2020 and suggests that the gang was heavily involved in all of them. This happens when Gary (Brian Huskey) audits the gang after the Paddy's Pub owners fail to repay several PPP loans.

Huskey's reactions to the gang's stories are priceless. He can't believe they were responsible for so many of the bad things that happened in 2020, although a montage shows they were completely to blame. Huskey appeared in Ant-Man as one of Cassie's school teachers, but his voice is more recognizable than anything else, as he's voiced various Bob's Burgers characters. He also appeared in Children's Hospital and People of Earth.

20 David Huddleston As Eugene Hamilton

"A Very Sunny Christmas"

One of the more surprising It's Always Sunnyguest stars occurred when the show creators brought in the other Lebowski from The Big Lebowski. Huddleston is best known for his role in the cult classic Coen brothers film as the billionaire that the Dude gets mistaken for, and his appearance in It's Always Sunny in Philadelphia might have become his second-best-known role.

The comedy legend plays Frank’s old business partner in the special "A Very Sunny Christmas," which sees him heavily involved in one of the gang's ridiculous schemes as he tries to convince Frank he's a ghost before threatening to kill Frank. Huddleston also played one of the Johnston brothers in Blazing Saddles. Sadly, It's Always Sunny was one of Huddleston's final roles. The episode was in 2009, and he only appeared in a Gilmore Girls episode before he died in 2016.

19 Pablo Schreiber As Ricky Falcone

"A Very Sunny Christmas"

Pablo Schreiber is best known for playing George Mendez in Orange Is The New Black, who was overly creepy and even had the nickname "Pornstache." However, he was a lot less creepy during his appearance on It’s Always Sunny, in which he played Ricky Falcone, a man whose toy robot had been stolen by Mac on Christmas many years ago. The appearance is in the It's Always Sunny holiday episode titled "A Very Sunny Christmas."

Mac feels guilty decades later and decides to return it, but he typically makes Eddie's life worse and even bullies him about his depressed lifestyle. They go on to try to buy toys for Ricky's children, but this only makes things even worse in the end. Being one of the earlier episodes, Schreiber is one of the most underused It's Always Sunny guest stars. On top of appearing in Orange is the New Black, Schreiber also appeared in Weeds, The Wire, Den of Thieves, and Halo.

18 Rob Thomas As Himself

“Dennis Reynolds: An Erotic Life”

Rob Thomas' appearance is one of the most random It's Always Sunny guest stars since he's a singer and not an actor. However, the celebrity’s appearance during season 4, episode 9, “Dennis Reynolds: An Erotic Life,” is one to — and it's one of the wildest casting decisions ever. However, considering the episode featured Dennis experiencing hallucinations and paranoia, it surprisingly makes sense.

The musician has since revealed how he got the gig, as Thomas invited the Always Sunny cast to a concert, which led to them offering him a part in the show. "We were just fans – and Matchbox was playing the Staples Center," Thomas said (via Audacy). "We just called their management and were like, ‘Hey, we’re big fans. You should come to the show.’ And they came early [and hung] out the whole day. We got drunk after the show together, and by the end, they were just like, ’You’re gonna be on the show.’"

17 Sinbad As Himself

“Dennis Reynolds: An Erotic Life”

Rob Thomas is one of the strangest It's Always Sunny guest stars, but what's even stranger is who guested alongside him. Along with Thomas, Sinbad, a comedian and actor who is best known for his role as Myron Larabee in the cult classic Arnold Schwarzenegger Christmas movie Jingle All the Way, featured in the same scenes.

In the episode, Thomas and Sinbad play two patients in a mental institution who harass Dennis. Sinbad hilariously kept reminding everyone in the episode that Rob Thomas was the lead singer from Matchbox 20. "That's Rob Thomas. Matchbox Twenty. Sing a song," Sinbad yelled. When Rob started to sing, Sinbad yelled, "Shut up!" While Rob Thomas was great in his role (especially with his facial expressions), Sinbad stole the show with his performance in this episode.

16 Geoffrey Owens As "Middle Aged Guy" (Possibly Himself)

"Frank's Pretty Woman," "The Gang Gets Invincible," "The Gang Makes Lethal Weapon 7"

Geoffrey Owens is one of the most interesting It's Always Sunny guest stars. He has appeared three times and plays an actor hired by the gang each time. The actor has played "Fake Tiger Woods," "Fake Donovan McNabb," and "Fake Don Cheadle" in several of the gang's schemes. Each time, he doesn't look happy to be there and is simply picking up a paycheck, which makes it that much funnier.

Though it isn't clear, Owens could very well be playing a fictionalized version of himself, as Mac and Dennis reference the fact that he starred in The Cosby Show. In real life, Owens played Elvin Tibideaux (the husband of Sondra Huxtable) in the sitcom. Fans might also Owens for his roles in The Good Fight, Power, and Ghosts. He also appeared in movies such as Fatale, Hide and Seek, and Ezra.

15 Dax Shepard As Jojo

"Ass Kickers United: Mac and Charlie a Cult"

Dax Shepard has played some pretty weird characters in his career, such as Frito Pendejo in Idiocracy and Vince in Employee of the Month, so it only makes sense that he'd have the weirdest role of his career when he became an It's Always Sunny guest star. It was a cameo in season 10, episode 10, "Ass Kickers United: Mac and Charlie a Cult," where he becomes one of the followers in the cult that Charlie and Mac ed.

Shepherd is great at playing dim characters, and his role as Jojo, a cult follower who religiously puts stickers on his face, is the epitome of exactly that. Dennis started the cult to make Mac stop eating all his cookies, but the ending for Jojo was hilarious. When a fire breaks out at Dennis and Mac's apartment, Jojo throws himself on it and is also seen riding a turtle through space. It ended up being a great role that many fans have already forgotten about.

14 Dennis Haskins As Coach Murray

"Charlie Got Molested"

Dennis Haskins as the lovable principal Mr. Belding in Saved By the Bell, and he was also one of the earliest It's Always Sunny guest stars. During his stint in season 1, episode 7, "Charlie Got Molested," Haskins plays the gang's old teacher, who was accused of molesting children. At this point, Mac wants to prove the former teacher is guilty and attempts to seduce the teacher by dressing in his old gym shorts.

They, of course, learn in the end that the teacher was innocent and was actually falsely accused of wrong-doing (which Charlie was saying all along anyway). Haskins's former co-star, Patrick Thomas O’Brien, coincidentally, also played a teacher in It's Always Sunny in Philadelphia season 2, episode 8, “The Gang Runs For Office.” Haskins also had cameos in other sitcoms, including New Girl and How I Met Your Mother.

13 Christopher Lloyd As Santa Claus John

"A Very Sunny Christmas"

Christopher Lloyd, who is an '80s icon and has starred in Back to the Future, Clue, Who Framed Roger Rabbit?, and ed Mandalorian season 3, has one of the best cameos of all the It's Always Sunny guest stars, as even fans of Back to the Future didn't recognize him. It's ironic that the most recognizable actor with the most prolific career of the best Always Sunny guest stars is so hidden that he's easy to miss.

The actor was hidden behind a white Santa beard in the “Always Sunny Christmas Special.” In a flashback scene, he visits Charlie's mother on Christmas, and this memory causes Charlie to react violently when he realizes who Santa really is. This causes Charlie to take all his frustrations out on a poor, unsuspecting Mall Santa Claus. This was a huge cameo guest role on It's Always Sunny, and it could have been given to a better actor.