On Dec. 25, Rod Shapiro and Pat Wong will exchange Christmas and Chanukah gifts spread under a seven-foot Christmas tree. They will listen to carols sung by Johnny Mathis and Chanukah songs by the Klezmatics. In the evening, this interfaith couple in their mid-50s, married two years, will light the menorah and invite friends to stop by their Long Beach home. Welcome to Chrismukkah 2005, a holiday that offers greeting cards that feature a reindeer with menorah antlers and recipes for Gefilte Goose and Kris Kringle Kugel in “The Merry Mish Mash Holiday Cookbook.” Christmas tree ornaments decorated with Stars...