That awkward moment when you're going to meet a friend in a public place and when you get there you saw somebody standing, facing back who looks like him. You cautiously come to him and try to scare him and found out it wasn't him, and the guy just stares at you probably thinking who this crazy girl is.
That awkward moment when you're having fun conversation with your friends and suddenly someone called your name behind you and come to you and talked as if she knows you for a long time, and here you are can't remember the girl. Trying to go with the flow with the conversation, says hi..., how are you?..., what are you doing here?... but try to end the conversation cuz you run out of words and just say I badly need to go cuz you really can't remember who she was and only later after you left you remember who she really was.