To make the filling, saute the onions in the olive oil until just soft, about 5 minutes. Add the chickpeas, walnuts, spinach, salt, pepper and lemon juice. Remove from the heat and set aside.
To make the pumpkin shell, combine the pumpkin, bulgur, flour, onion and seasonings and mix well. Set aside for 10 minutes to let the bulgur soften. If the dough appears dry, add a few drops of water and knead well.
Here's a tricky part....To shape the kibbeh, knead about 2 Tbsp. of the pumpkin mixture until it holds together. Keeping your hands moist, form a smooth football-shaped oval. Stick your thumb into one end and turn the ball between your thumb and forefinger to create space inside for the filling. Fill the space with 2 tsp. of filling. Pinch the end of the football closed and gently roll to reshape if necessary. Repeat until all the dough and filling is used.
Using a deep saute pan, add enough vegetable oil to come no more than 1/3 up the sides. Heat until a deep fat fry thermometer registers 375 degrees. Using a tablespoon, carefully slide the balls into the oil, three or four at a time. Don't crowd them in; fry for 2 minutes or until golden brown. Drain on paper towels. Repeat in batches until all are fried.