Christmas Crasher
A person who is not Christian and who normally does NOT celebrate Christmas, but yet enjoys the holiday of Christmas, gets the day off, goes to Christmas parties, enjoys eggnog, sings Christmas songs and hangs out with his/her Christian friends around the Christmas tree and even receives gifts from Santa.
I'm a Jew, but yet I'm a Christmas Crasher because I love to go to my buddie's Christmas party, drink lots of spiked egg nog, get gifts under the tree, sing Christmas carols and enjoy the day off from work!