This Sunday, December 9 at 8pm on FOX, "The Simpsons" hometown of Springfield collides with Portland in "The Day the Earth Stood Cool." Fittingly, the episode, guest-stars "Portlandia" creators Fred Armisen and Carrie Brownstein as hip parents who move in next door to The Simpsons, causing all sorts of "we're not cool enough" chaos for the classic TV family.

I jumped in on a conference with Armisen, Brownstein and "Simpsons" executive producer, and writer of the episode, Matt Selman to talk the genesis of the Portland-focused story, how the "Portlandia" crew got involved, and what it's like to work with Homer Simpson.

According to Selman, it took three years to make a "Simpsons" episode focusing on Portland's "hipster" culture. The initial idea was to tell a story that would move The Simpsons from Springfield to Portland--a place that Lisa would expect to be her Utopia. But she would be in for a rude awakening when she realized that the rest of the family loved it, but she couldn't stand it. Selman said the idea was based on former-"Simpsons" producer Bill Oakley who moved to Portland, (and now works on "Portlandia") only to discover that it wasn't all he dreamed it would be. Selman said, "He's one of those guys who moved to Portland thinking, 'oh this place will solve all my problems, this is a cool city I can live in, unlike uncool L.A.,' and then he just tweets all day about weirdos that make him irritated." Selman continued, "Lisa would go through the journey of Bill Oakley," emphasizing, the theme of never being able to escape your problems. But, unfortunately/fortunately, "Portlandia" came about during the three year planning phase of this episode and depressed Selman, because, as he said, the show already did what he was hoping to do, but funnier. "'Portlandia' was eight million times than anything we could've ever done," he said. So he shifted his focus and thought, "What if the Portland vibe came to Springfield?" He continued, "so you're not going against 'Portlandia,' you're going with 'Portlandia.'" And thematic focus shifted as well, from escaping one's problems by moving, to "does one have to give up being cool to be a parent."

Which brings us to Armisen and Brownstein. They play the aforementioned cool parents who turn Homer and Marge's world upside down with their hipstery, natural-living, Portlandian ways. Armisen's character, Terrence, runs a donut shop that bares a striking resemblance to Portland's famous Voodoo Donuts, and obviously that pops up on Homer's, donut-loving radar. Terrence and Emily (Brownstein) are the types of parents who can remain on the cusp of all things cool without sacrificing any of their own interests for the sake of parenthood. While Homer and Marge have done noting but the opposite. The duo were specifically asked to play Terrence and Emily, to the delight of both Armisen and Brownstein. "Who hasn't been a fan of 'The Simpsons'?" Armisen said, while celebrating how funny the script was. "I distinctly recall in the email exchange between Fred and I, following us being asked, it was just full of exclamation points. We were very excited and flattered and everything, it just only hyperbole and ecstasy, we were very honored." She added, "We were very humbled and starstruck to be in the same room as Dan [Castellaneta]." The experience was very surreal for both "Portlandia" stars, she said. "We just kept turning to each other to be like, 'I have a scene with Marge!'"

Brownstein's Emily butts heads with Marge over the philosophy of naturalistic mothering, especially when it comes to breastfeeding. Due to Emily's pro-breastfeeding ways and beliefs, Marge begins to feel shame for only bottle-feeding Maggie. "There's kind of a culture clash there," Selman said. "Marge is being made to feel subtly insecure for not being as good a mom."

"Simpsons" creator Matt Groening is originally from Portland and when asked if that had an impact of this story Selman said it did, but only when the story was originally conceived. But once Armisen and Brownstein came on board, that all changed, since Portland was now coming to Springfield and not vice versa.

Selman revealed that he was secretly hoping Armisen and Brownstein would play his hipster parents, and was so thrilled to be working with the duo that he hopes to have them back in future episodes, which he unofficially offered to them. Would they?

"We're already saying yes," Brownstein said, "we're saying yes right now."

Patton Oswalt brings the funny to the episode too, playing Terrence and Emily's son, T-Rex, who turns out to be an obnoxious and pretentious new friend for Bart. Also, folk rockers The Decemberists bring that heady, Portland-y sensibility as well. The band composed original music just for the episode.

"The Day the Earth Stood Cool" airs on Sunday Dec. 9 at 8pm ET on FOX.