#1) Top of hat red instead of green on right elf.

#2) Right elf has a missing eye.

#3) Green triangle instead of purple on hat of left elf.

#4) Missing button on keyboard.

#5) Left elf has a blue collar instead of green.

#6) Left elf has one finger more.

#7) Right elf has an extra line on his suit.

#8) Right elf has a missing circle on his boot.

#9) Left elf has an extra line on his boot.

#10) Left elf has different red-green pattern on his boot.

#11) Left elf has the number 6 in his ear.

#12) Right elf has a square intead of a circle on his boot.

#13) Left elf is missing his mouth.

#14) Right elf has one green leg intead of purple.

#15) The words "Merry Christmas" written on the computer screen (monitor).