Rinse the grapes, blueberries, and strawberries under cool water. Let them drain well, then pat them dry with paper towels. Dry fruit sticks to the tray better and keeps your design neat.
Peel all 12 clementines and pull off any stringy white pith. Split each one into wedges with your fingers. I like to set them in a bowl first so I can grab them quickly.
Start at the outer edge of the platter and lay the wedges in tight rows. Work inward until no tray shows through. This orange layer is your pumpkin, so fill every gap.
Cut the strawberries in half from top to bottom. Lay the halves in a curved line near the bottom of the pumpkin. Tilt the curve upward at the ends for a big, happy grin.
Place the blueberries in the center of the orange wedges. You can shape them into a small circle or a triangle. I prefer the triangle because it looks like a classic jack-o'-lantern nose.
Arrange the red grapes into two equal circles above the nose. Keep both circles the same size so the face looks balanced. Stand back and check that the eyes sit evenly.
Slice the Granny Smith apple into wedges. Tuck them at the top of the tray so they form a stem. Serve right away, or chill the tray until the party starts.