The FXX sitcom returns for season 15 on Dec. 1.

"As long as it's funny, I'll do it."

That's been Kaitlin Olson's unofficial motto for 15 seasons and counting on It's Always Sunny in Philadelphia, which will become the longest-running live-action sitcom, by season count, in American television history with its Dec. 1 return on FXX.

Sunny may be a comedy, but portraying the bird-like Dee often turns into one of the most dangerous jobs on TV, considering Olson has been set on fire, drowned, and hit by a car — multiple times. "I think they're still trying to cover all the bases," she jokes. Well, they found another one in season 15 when the gang takes an extended trip to Ireland (though COVID-19 meant California had to serve as a stand-in).

"We shot an episode this season where Dee sinks in a bog, which I was very excited about, because it sounds hilarious," shares Olson when asked by EW to pick her wildest day of filming. "I also knew it was going to be miserable, which most of my hilarious things are."

"They built a bog in a swampy area at the Disney ranch and filled it with some material that was supposedly safe," Olson explains. "I kept going, 'What is this made of?,' and they're like, 'Don't worry, it's organic!' Great. So, whatever got in every single orifice of my body was organic. It's the middle of the night, freezing cold, and I have to come out looking like a crazy swamp creature and run off into the woods. Right before we shot, the AD came over and said, 'When you come out, just be really careful because there are a bunch of holes in the ground. Don't step in them. And also stay really close to the bog, otherwise you'll run out of the shot and we won't be able to use it.'"

Kaitlin Olson
| Credit: Prashant Gupta/FXX

Olson continues, "I go under, come up, open my eyes, and they fill up with whatever this bog is made of. I can't see anything, I could barely walk, I'm trying to remember where the holes are, I half-scream my lines. All I'm thinking is, 'I'm not doing this again, so don't trip and ruin it.' Of course I nailed it on that first shot, thank you very much... I had Charlie [Day] with me, and he guaranteed that it was funny, so I was like, 'Great, we can go home.' And that was my most excruciating day on set this season — and there's something like that every year."

In addition to Olson's bog dive, fans should expect Sunny to satirize the last two years like only Sunny can. "This season was particularly fun because we had 2019 and 2020 to write about, and so it's quite a season," she adds. "I read the scripts and was squealing with delight; it's so much fun. We had a lot of good material out in the world. Our first episode is called '2020: A Year in Review,' and it's wild. [Laughs] People are going to love it and hate it."

It's Always Sunny premieres Wednesday at 10 p.m. ET on FXX.

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