Off to wonderland they go! Continuing their tradition of family Halloween costumes, Neil Patrick Harris and his fiance David Burtka dressed up as Tweedledee and Tweedledum from Alice in Wonderland. Their three-year-old twins, Harper and Gideon, looked adorable as Alice and the White Rabbit. “Our costumes for the Halloween carnival at the kids' preschool yesterday. But 10/31 will be frighteningly different..! @DavidBurtka came up with both themes/costumes. He's amazing," the How I Met your Mother actor posted on Oct. 20.