Put the cream cheese, Cheddar, onions, salsa, cumin and jalapeno into the bowl of a mixer, and blend thoroughly. Form into a pumpkin-like shape, and refrigerate until firm, about 2 hours.
Before serving, roll the cheese ball in the crushed Doritos. Arrange the cheese ball on a plate, and press the bell pepper stem into the top - it should like a mini pumpkin stem.
You can serve the pumpkin as-is, or break off pieces of black bean chips to form a Jack-o'-lantern face. The chip pieces should adhere to the pumpkin cheese ball if you gently press them onto it, but you can also stick them on using a very small dab of the cheese ball mixture on the back of the black bean chip features; this will act like glue. Serve the cheese ball with black bean chips, crackers or crudites.