Saturday Night Live and Portlandia personality Fred Armisen co-hosts This American Life with Ira Glass. This week&amp;#8217;s theme: doppelgangers. Armisen imitates Glass through the hour-long show, something Armisen worked on for SNL, &ldquo;but the public radio personality isn&rsquo;t quite famous enough to be mocked on network TV,&rdquo; according to TAL&rsquo;s website. -L 
Photo by Adrianne Mathiowetz