Heat a medium-sized skillet over medium heat. Spray with cooking spray.
Add ground beef to hot skillet and stir in taco seasoning. Cook until beef is no longer pink, stirring frequently to crumble.
Dice bell pepper and drain and rinse beans; add both to the beef. Stir to combine and cook until heated through.
Slice olives and avocado; thinly slice cheese, making one jagged edge to resemble teeth.
Optional: Cut Halloween shapes out of tortillas and bake in the oven until just barely crispy.
Divide shredded lettuce among 4 serving bowls; add in meat mixture and top with veggies, sour cream, cheese, and tortilla shapes (if using), forming fun monster faces.