My date got the keys to my car from my parents and proceeded to fill it up with balloons and crumpled up newspaper while I was at swim practice after school. Sign on my car said "somewhere in this crumpled mess is my answer, no or yes",

In the trunk were 2 boxes of lucky charms scattered with a sign that said "I'm lucky such a charming guy asked".

One year I remember heart attacking my date's car and put a sign on it that said something like "it would make my heart pound if you would go to the prom with me"

There was another one that was a girls choice where if my answer was yes I had to wear some really goofy hat she left me the next day to the class we had together - made for some fun laughs when I walked in.