According to TV Guide, Pell, who plays Paula Hornberger on '30 Rock,' will appear as Tammy Zero early in Season 4.
Patricia Clarkson will appear in Season 4 as Tammy 1, Ron's first ex-wife. Megan Mullally, Offerman's real-life wife, has made several appearances as Tammy 2, Ron's second ex-wife named Tammy.
Can Pawnee handle three different Tammys? We'll see on Sept. 22 when 'Parks and Recreation' returns to NBC.
In other casting news ...
Morgan Fairchild is heading to 'Bones.' Fairchild will play Bianca, the CEO of a toy company. After an employee's remains are discovered, somehow Bianca becomes involved. [TV Guide]
'Smallville' actress Cassidy Freeman has joined the cast of 'The Playboy Club.' Freeman will play Frances Dunhill, a socialite who begins seeing Nick Dalton (Eddie Cibrian) for publicity purposes. [TVLine]
Alex Steele is returning to 'Degrassi,' but not as Angela. Steele, who played Angela Jeremiah on Seasons 1-5 of the hit teen series, will return as Tori, a new character. Tori believes she's the best at everything and has never heard the word "no." Steele's sister, Cassie, played Manny Santos on the show from Seasons 1-9. [EW]