Do people become aggressive after they had surgery?

Generally after surgery people are just tired and nauseous. Some patients wake up with the "thankful to be alive" feeling. Most children (and some adults) cry for a while afterwards - the children because they are scared, and the adults because they are scared or relieved. Being aggressive after surgery is a bit more unusual. I've added a related link to an article about post-operative delirium (which includes aggression) which you may be interested in.