Merry Christmas in Klingon:
QISmaS Quch Daghajjaj

Merry Christmas in Elvish:
N merye i turuhalmeri!

Merry Christmas in Binary Code:
01001101 01100101 01110010 01110010 01111001 00100000 01011000 01101101 01100001 01110011 00100001

Merry Christmas in Esperanto:
Gajan Kristnaskon

Merry Christmas in Latin:
Natale hilare et Annum Faustum

PS. I can’t find how to say Merry Christmas in Na’vi (from Avatar movie) because there is no Christmas in the film, and that phrase has not been developed…..yet. If someone finds it – please let me know. And feel free to try and make it up yourself! -Na’vi language-

So……

01001101 01100101 01110010 01110010 01111001 00100000 01011000 01101101 01100001 01110011 00100001!!!!!!