In the 20 years that It’s Always Sunny in Philadelphia has been on the air, the show has welcomed a variety of guest stars. “Rowdy” Roddy Piper appeared as a homeless wrestler named Da’ Maniac in a couple of episodes in the earlier seasons. Comedian Sinbad, Matchbox Twenty singer Rob Thomas, Breaking Bad stars Bryan Cranston and Aaron Paul, and even Diddy have all shown up at different points as well. But there are a few people who have been involved with the series, both behind and in front of the camera, who weren’t quite as obvious as all the others. Here are a few contributors you might have missed.Fred SavageBest known for playing Kevin Arnold on The Wonder Years, Fred Savage is credited with producing and directing more than a dozen episodes of It’s Always Sunny in Philadelphia between 2007 and 2009. He told GQ in 2012 that he thinks he got the job because creator Rob McElhenney (now known as Rob Mac) loved The Wonder Years and asked Savage a bunch of questions about it after hiring him. Savage was also an Always Sunny fan, and since the show was looking for directors at the time, it was a perfect match. The first episode he directed was Season 3’s “The Gang Gets Invincible,” and his last credit was for the Season 6 episode “A Very Sunny Christmas.”Christopher LloydSpeaking of “A Very Sunny Christmas,” it’s in that same episode that Danny DeVito’s former Taxi co-star Christopher Lloyd makes an uncredited cameo appearance. As Charlie (Charlie Day) tells Mac (McElhenney) about his mother’s tradition of having multiple Santa Clauses come to the house with presents on Christmas morning, they realize that Charlie’s mom might’ve been a prostitute. One of the Santas in the flashback sequence is a cleverly disguised Lloyd. See if you can spot him in the clip below.Guillermo del ToroFrankenstein director Guillermo del Toro also made a couple of unrecognizable cameos on Always Sunny as Pappy McPoyle, the patriarch of the incestuous McPoyle family. Del Toro was such a big fan of the series that he cast Charlie Day in his 2013 movie Pacific Rim. During the film’s production, he asked Day about doing a cameo on his show, so they finally came up with a character for him. Del Toro first appeared as McPoyle in Season 8’s “The Maureen Ponderosa Wedding Massacre,” and reprised the role in the Season 11 episode “McPoyle vs. Ponderosa: The Trial of the Century.” Del Toro loved playing the character so much that he even pitched an entire series to FX called Those Crazy McPoyles. Take a look at Del Toro as McPoyle below.The creators of Game of ThronesRob McElhenney isn’t just a big fan of The Wonder Years; he also loves Game of Thrones. It’s for that reason that he hired Thrones creators David Benioff and D.B. Weiss to write the Season 9 Always Sunny episode “Flowers for Charlie,” in which Charlie participates in an experiment that makes him smarter. Benioff and Weiss also appeared as lifeguards in Season 12’s “The Gang Goes to a Water Park.” McElhenney later returned the favor by appearing in the Season 8 premiere of Game of Thrones, where he was promptly killed with an arrow to the eye.The post 5 Celebrities You Didn’t Know Worked on ‘It’s Always Sunny in Philadelphia’ appeared first on VICE.