Zombie Cliché Lookout:
In zombie stories you often have a character who either doesn’t notice that a person is clearly dead, or simply refuses to believe it. They will invariably rush out to greet this person, attempt to talk to them, or see if they need medical assistance (zombies are, after all, not known for their dexterity and healthy appearance). The results are generally predictable: they’re bitten and turn themselves, or someone who is paying a little more attention intervenes and prevents disaster.
These events typically happen at the beginning stages of the outbreak, before everyone takes Zombies 101 at the school of hard knocks. Occasionally this trope will show up later, usually following the death of a loved one when the survivor is too wracked with grief to face reality.