Head to the North Pole and enter the Toy Factory at (9,11).
In Toy factory walk to (18,6) and enter Santa's room.
In Santa's Room walk to (12,0) and enter Raindeer Pen.
Speak to Elf and he will tell you that Penguins came out of nowhere and chased the elves away.
Agree to help him then head back outside to 4-2 and kill 100 Penguins.
If you kill anything other than a penguin it will take away from your penguin kill counter.
Once you have 100 kills head back to Elf and he will give you instructions on where to receive your reward.
Go back outside and say "Merry Christmas" to the tree to claim your reward.