Bottom line: an iTunes card is an acceptable last minute gift idea or unexpected surprise present. A dog is not.
In its annual press release reminding people not to be irredeemably stupid and buy a dog without careful forethought, Dogs NSW makes the point that a pet can be a great Christmas present, providing you've thought it through first. As vet Dr Peter Higgins puts it:
Puppies shouldn't be chosen as a last minute present to make children smile on Christmas day, but that doesn't mean bringing one into the family as a Christmas present is careless. So long as you consider what you want from a dog and choose the breed accordingly, they can become very important members of the family. Buying a dog as a family Christmas present is not irresponsible, but buying one as an impulsive gift is, and can have serious consequences.
If you do have a dog, don't forget to buy them a present. I usually favour something edible for the "instant gratification" factor.