In its sophomore season, Parks and Recreation has really hit its stride and finally become the hilarious half hour it always had the potential to be. Now it's about to get even funnier: Amy Poehler's husband, Will Arnett, is going to guest star on the show in January. He'll only be on one episode and will play an MRI tech, ostensibly at the hospital where Ann works.The hotness doesn't end there: Justin Theroux is also joining the cast, but unlike Arnett, his will role will be as a major recurring character. He'll play an old friend of Ann's and love interest for Leslie, first appearing sometime early next year. So basically Amy Poehler is the luckiest girl onscreen and off.