In a slow cooker, combine the cream cheese, shredded cheddar cheese, mayonnaise, grated Parmesan cheese, diced green onions, minced garlic, fresh lemon juice, Old Bay seasoning, paprika, salt, and pepper. Mix well until all the ingredients are evenly combined.
Stir in the chopped and cooked shrimp, making sure it is thoroughly mixed in.
Cover the slow cooker and cook on low heat for approximately 2 hours, or until the cheeses are melted and the dip is hot and bubbly. Stir occasionally during cooking to prevent sticking.
Once the dip is heated through and the cheeses are fully melted, give it a final stir to combine all the flavors.
Taste and adjust the seasonings, adding more salt, pepper, or Old Bay seasoning if desired.
Serve the cheesy shrimp dip directly from the slow cooker, keeping it on the warm setting. If you want a brown cheese top, broil in the oven just before serving.
Provide tortilla chips or crackers alongside for dipping. Enjoy!