The type of person who will ask you a thousand questions about a party you're throwing, ask for your address the day of the party, ask the best route to get there, etc. They just can't reply 'yes' to the invite, they have to talk to other people and are essentially snooping around for info about the party. But sometimes they just happen to be your friend.
Dude, stop asking so many questions, you're a fuckin' party snooper. Actually, you're uninvited.