Although Papyrus is a nice girl, she isn't very bright is she?
me: Papyrus, there is one extremely obvious flaw when it comes to your plan!
Papyrus: what do you mean human?
me: look, you're really sweet and I like you so, to put it nicely, the extremely obvious flaw is extremely obvious. you do not, in your note, put "little do you know this is a trap so I can capture you" and you definitely do not sign it. that's why you never capture anyone!
okay human, now that makes sense.
me: c'mon, let's get you home.