Weedling is to find your way into a party you have not been invited to by any method. It can involve climbing a fence, but mainly refers to the act of repetitively asking the person having the party if they can go/guilt tripping people into an invite. People who often do this can be known as weedlers. However at the party weedlers do not mingle, they stalk and follow, clinging onto the few they know at the party.
Joe - "Mark," has weedled his way into another party.
Dylan - Weedling fuck! How did he manage it this time?
Joe - He sent "Eddy" on a guilt trip, told him to remember "how they were best mates four years ago."
Dylan - That guys nothing but a pathetic weedler.