How to awaken cat

It's really fun how cats respond to this. If a cat has been operated on in my vet and doesn't want to wake up I always hold a can A/D in front of their noses. And after a few seconds their heads are up and eating.

You can see the pupils expanding

Aww that's so mean D:
...but funny...
-opens a can of tuna and walks up to my sleeping cat-

Waking up to disappointment

There's a picture of a dog on the can.