Everybody knows the President's Secret Service code name, of course. (It's "Rawhide.") Nancy's is leaking out, so Ear may as well spill that, too: "Rainbow." But best of all, darlings, is White House Social Secretary Muffie Brandon's. It was spanking-new for the last trip out West: "Tablecloth." (Remember the White House's terrible tablecloth crise?) Heh-heh . . . Twittering at Children's Hospital. During the Great Wind a week or so back, two sparrows blew in. They've set up house atop the gigantic Rauschenberg mural there. ("Periwinkle Shaft"--it's swarming with lizards, horses and fun-house mirrors, but wasn't built for birds.) The happy couple perches atop the painting--adding to the impasto, oh dear. Staffers are frantic, hygiene-wise. The Audubon Society's scratching its head. (You know those bird men.) The word "Sparrowhawk" has not yet been breathed . . . And Ear hears what didn't get displayed at the White House Easter Egg Roll, along with the Alice-in-Wonderland cutouts: Two 10-foot-tall Nancy and Ronnie cutouts. These are based on the First Paper Dolls. (Don't you just love yours, in their star-spangled undies?) The artistes at the Corcoran School of Art don't know what to do with them now. But they're thinking hard. Oh, dear . . . And the Internal Revenue Service kicks off its Blood Drive April 15. Ear just thought you might like to brood about it.