Jennifer Garner on Filming 'Party Down' Magic Mushrooms Scene Without Personal 'Experience' (Exclusive)

The actress spoke with ET at the 'Party Down' premiere in Los Angeles on Wednesday.

Jennifer Garner isn't afraid to step outside her comfort zone for comedy. The actress joined the new third season of the cult comedy classic Party Down, and one particular episode called for her character to trip out on magic mushrooms -- which was an experience she's not particular familiar with.

"I haven't seen the episode," Garner told ET's Will Marfuggi on the carpet at the Los Angeles premiere of Party Down's third season on Wednesday. "It was terrifying -- any time I have to play inebriated, or any altering anything -- to me. I don't have a lot of experience."

"But Ken Marino really held my hand, and he was an amazing director," Garner added with a smile. "He really made me feel as good as one can feel when they are standing on their head."

Marino both directed an episode of the third season and stars in the series, alongside returning cast Adam Scott, Jane Lynch, Megan Mullally, Ryan Hansen and Martin Starr. 

When asked what made he want to be a part of the series -- which is returning nearly 13 years after the show originally went off the air -- Garner exclaimed, "They're legends."

"This is a group of legends. There's no one funnier. There's no writing that is better, more sparkly, more naughty, more fun," she marveled. "I could not jump in it fast enough, honestly. I was so, so excited to be invited."

Garner is also one of several big-name guest stars, alongside Quinta Brunson, Nick Offerman, James Marsden, Bobby Moynihan to name a few.

The long-awaited third season of Party Down premieres Feb. 24 on Starz.