Place the softened cream cheese, shredded cheddar, finely chopped onion, salsa, and ground cumin into a large mixing bowl.
Blend thoroughly with a sturdy spoon or hand mixer until the ingredients are evenly incorporated and the cheese mixture has a smooth, uniform consistency.
Spread a large sheet of cling wrap over a flat work surface, then transfer the prepared cheese mixture to the center.
Bring the edges of the plastic wrap upward around the mixture and twist them together at the top to enclose it securely. Gently shape the wrapped mixture into a rounded ball.
Lightly mold the surface to form subtle ridges that resemble the natural contours of a pumpkin.
Refrigerate the wrapped cheese ball for a minimum of 2 hours. Chilling allows it to become firm enough to retain its shape while also giving the flavors time to combine.
Remove the chilled cheese ball from the refrigerator. Carefully peel away and discard the cling wrap.
Roll the cheese ball in the crushed nacho cheese tortilla chips, pressing gently as necessary so the crumbs cover the exterior evenly and produce a bright orange, pumpkin-like finish.
Insert the stemmed top of the bell pepper into the center of the cheese ball to complete the pumpkin appearance.
Set the finished pumpkin-shaped cheese ball on a serving platter.
Arrange crackers, pretzels, corn chips, and fresh vegetables around the cheese ball for dipping and spreading.
Serve immediately.