I'd say it's mostly inspired by bad public access tv, Todd Solondz, commercials, lo-fi video, cheesy character graphics (think star wipes), and paint thinner. The commercials they do spoof on the impracticality of most consumer products, and are undoubtedly conceived by Bod Odenkirk,who has been doing infomercial parodies since at least Mr. Show (another quirky, pioneering show with a cult following.)
Even though it is hit and miss, I really like how unfiltered and original it is. The recent "Ohh Mama..." sketch where Tim and Eric repeatedly scream that phrase and bash a laundry basket into the floor to the sounds of eerie, twinkly music and audio distortions while their vaguely androgenous mother looks on lovingly really exemplifies these qualities. It's not always funny, is ostensibly random, but nevertheless evokes strong reactions rather than boredom. It's artsy, but hides it behind advertisements for poop vacuums. The fact that they mostly use normal people for actors is also pretty cool. And John C. Reilly's involvement gives it the all-important hipster stamp of approval. "Last resort!"