This is simple and can be adapted with onion, green pepper, beef, etc.
thin spaghetti noodles (the same amount you would use if you were having spaghetti for dinner)
1 can/jar spaghetti sauce
1 jar pizza sauce
1 1/2 cups Cheddar cheese
1 1/2 cups mozzarella cheese
Cook and drain noodles.
Layer half the noodles, half of each sauce, half the cheeses, half the pepperoni, repeat layers.
Cook in crock pot for 2-4 hours (no more) or bake at 350 degrees for 30 minutes.