Preheat your oven to 325°F (163°C).

In a large mixing bowl, combine the imitation crab meat, half of the mozzarella cheese, half of the Colby Jack cheese, diced celery, sour cream, the white parts of the green onions, cream cheese, mayonnaise, Worcestershire sauce, lemon juice, and garlic salt. Mix everything together smoothly.

Grease an 8x8 casserole dish with cooking spray or butter. Spoon the crab mixture into the dish, spreading it evenly.

Layer the remaining mozzarella and Colby Jack cheese over the top of the crab mixture.

Place the casserole in the preheated oven and bake for about 20 minutes, until the cheese is golden brown and bubbly.

Once baked, remove from oven and allow to cool slightly. Sprinkle the green parts of the onion on top and serve warm.