Slice the top off each apple like you're prepping a tiny pumpkin, and set the tops aside. Use your melon baller to scoop out the flesh, leaving the walls thick enough to hold their shape. Brush the inside with lemon juice so the flesh doesn't brown before baking.
Grab your paring knife and carve simple triangle eyes and a jagged mouth into each apple, just like you would with a real pumpkin. I like keeping the cuts small and shallow the first time, since you can always widen them later. Kids can help here with a butter knife under supervision.
Warm the peanut butter in a small saucepan over low heat until it turns smooth and pourable. Stir in the date paste and pumpkin spice until fully combined. The mixture should look glossy and blend easily into the hollowed apple centers.
Spoon the warm peanut butter mixture into each carved apple, filling it about halfway. Place the tops back on and set the apples upright on a parchment-lined baking sheet. Bake at 350°F for 10 minutes so the filling softens and the apple edges start to caramelize slightly.
Pull the tray out, remove the tops again, and spoon granola generously over the warm filling. Slide the tray back into the oven for another 10 minutes so the granola turns golden and slightly crisp. This second bake is what gives the bites their satisfying crunch.
Let the apples rest for about 5 minutes once they're out of the oven, since the filling stays quite hot. Set the carved tops back on at a jaunty angle for that classic jack-o-lantern look. Serve them right away while the granola is still crunchy and the filling is warm.