Holly Jolly Christmas: Your character is stuck laughing uncontrollably, no matter the situation, for the next three hours.
Grandma Got Run Over By a Reindeer: You character has amnesia for 24 hours.
Silent Night: Your character is mute for six hours.
All I Want for Christmas is You: Your character is obsessively love with another character (anon specifies) for two days.
You're a Mean One, Mister Grinch: Your character is hateful and bitchy for twelve hours.
Feliz Navidad: Your character can only speak in Spanish for three hours. (If necessary, use a translator.)
Angels We Have Heard on High: Your character sprouts angel wings and has them for the next twelve hours.
Chestnuts Roasting on an Open Fire: Your character is a glutton for six hours.
God Rest Ye Merry Gentlemen: Your character is groggy and not very attentive for the next three hours and won't pay attention to much if anything at all.
Jingle Bells: Your character is only able to speak in rhyme for the next fours hours and has to do so in some type of song format.
Frosty the Snowman: Your character wears a magic hat for the next twelve hours and is able to animate any inanimate object no matter what it is.
I saw Mommy kissing Santa Clause: Your character is attracted for the next five hours to whoever puts "Mistletoe" in their inbox.
12 Days of Christmas: For 12 hours, your character wants to give everyone gifts
Feel free to add more!