Set barbecue grill to medium heat.
In a bowl, mix together beef, the juice of half a lime, 1 tablespoon garlic, 1/2 cup diced onion, cilantro, and chili powder. Make 4 patties.
Grill burgers, flipping once, until cooked to desired doneness. During the last minute of cooking, top burgers with cheese (optional); let melt. (See below for instructions on “cheese teeth.”)
Toast KING'S HAWAIIAN Original Hawaiian Sweet Rolls if desired. Assemble burger using desired amount of guacamole. Lettuce, tomato, grilled onions, etc. are always an option.
To make teeth or fangs, start by cutting cheese slices into triangular pieces. Lay the cheese over the hamburger patty with the sides hanging over. If you like more cheese, make more teeth!
For the monster’s eyes, cut limes and cherry tomatoes in half. (Key limes work best because they are smaller.) Secure cherry tomato in the middle of the lime with half of a toothpick. Then secure lime and tomatoes into the top bun with toothpicks, placing the eyes in the front center portion of the bun.
To make jalapeño horns, cut the stem off of a jalapeño pepper and then cut in half, longways. Use toothpicks to secure the pepper “horns” onto the top bun, placing them just behind and outside of the eyes.