Animal Care and Control is going door-to-door in Altadena, checking on current licensing for both dogs and cats.
If you're late to the the license-party, download a form here. For dogs, you'll need to include verification of a current rabies vaccine. And if your dog is not yet spayed or neutered, think about it. Licenses must be renewed every year, and the fee for an unsterilized dog is $60, as opposed to $20 for one that has been spayed or neutered.