Saturday Night Live alum Tina Fey will trade in her Sarah Palin impersonation to appear on pay-per-view and video on demand as NBC Universal (www.nbcuni.com) premieres her theatrical comedy film Baby Mama on cable and satellite systems Oct. 8.img src="http://feeds.feedburner.com/~r/MultichannelBreakingNews/~4/413144887" height="1" width="1"/