Liza Minnelli is having a stay-cation in New York, taking in the sights and visiting friends. The icon saw Broadway’s “Pippin,” and this weekend she surprised the Rockettes backstage at the Radio City Christmas show. Liza also took in Michael Feinstein’s holiday show at Birdland. We’re told she plans to return to catch Billy Stritch, whom she’s toured with since 1991. They’ll appear together Feb. 16 at the Fort Lauderdale Broward Center for the Performing Arts, where Minnelli kicks off her 2014 tour.