Calvin and Hobbes by Bill Watterson for December 21, 1990
Susie: Plotting to hit me with a slushball, eh? Well, here! Calvin: See that? See that?! She hit me first! Now if I hit her, it's justified! Ha ha ha! Sweet revenge! Oh boy! Oh boy! Hobbes: ...Or you could prove to Santa how good you are. It's your big chance... Calvin: I don't want to be this good!