He doesn't have what you'd call a famous face, but radio icon Ira Glass's distinctively nasal voice and meticulously casual cadence are unmistakable to the couple of million devoted public radio listeners who comprise his weekly audience. On Sunday, Glass's formerly Chicago-based program "This American Life" (which was for a decade headquartered at the studios of Chicago's WBEZ, until Glass and his gang moved to New York in 2006 ) will feature a guest host -- "Portlandia" (IFC) and "Saturday Night Live" star Fred Armisen.

Or so the scuttlebutt goes.

This American Life's web site specifies only "a public radio personality, one familiar to This American Life listeners." But who else would Armisen imitate? David Sedaris? Jonathan Goldstein? Sarah Vowell? Not likely. His impersonation was initially developed for SNL, Armisen told Entertainment Weekly, but the subject of his skewering "isn't quite famous enough to be mocked on network TV."

According to his official NBC bio, Armisen "began his career as a musician in the Chicago-based post-punk band Trenchmouth as well as playing with Blue Man Group." So there's that.