Hot glue bows on the top of the pumpkin, or on the bottom when you're doing a bowtie.
Take the temples off the glasses frames and hot glue the nose piece of the glasses to the front of a pumpkin.
Take a hat and put hot glue around the inside edges, then carefully place it on top of the pumpkin. Allow to cool. Add if desired a silk flower to it with hot glue, if desired.
Add a little costume mustache.
Video
Notes
Pro Tip: Use gorilla glue hot glue sticks. They are the strongest hot glue sticks I have found and the accessories will stay on your pumpkins a lot better with a strong glue.