In the weeks leading up to Thanksgiving Kate became enamoured with A Charlie Brown Thanksgiving and could be found scripting entire scenes at a time. Her favorite scene was the one in which Charlie Brown prepared a feast consisting of toast, popcorn, pretzel sticks, and jelly beans for his friends. Gonzo's mom heard about Kate's fondness for this particular scene and thought she would surprise Kate with a feast of those items.
Upon arriving at Grandmom's house, Kate announced that she was hungry. She made her way over to the table and eyed up the spread. Within earshot of the entire family Kate exclaimed in a startling accurate rendition of Peppermint Patty's voice, "What blockhead cooked all this?!"
The entire family, Grandmom the Blockhead included, roared, thus reinforcing the behavior. Therefore, "what blockhead cooked all this" has become a favorite phrase, uttered over and over and over.