The IFC sketch comedy series features Armisen and Carrie Brownstein satirising hipster culture in Portland, OR with the help of guest stars Kyle MacLachlan, Aimee Mann and Jack White.
Speaking to ET Online, Armisen said he is heartened that Portlandia has developed such a devoted fanbase.
"It's like the ultimate surprise. Even though Carrie, [producer] Jonathan [Kristel] and I are very ambitious and work-oriented and try to make the best show we can, we still took everything in little steps," he admitted.
The actor further explained: "[Our process] was, 'Let's see if we can make this pilot. Let's do six episodes'. It was very much step-by-step. As a result of that, we never took anything for granted, and we still don't.
"I always assume people on the street are going to bring up SNL to me, but it's now a lot of Portlandia, and that's really nice."
Portlandia's third season features guest appearances from Rose Byrne, Roseanne Barr and Little Britain's Matt Lucas.
The series airs Fridays at 10/9c on IFC. Watch a clip from the show below (US only):