Preheat oven to 450° F.
Finely chop crab meat, celery, parsley, onion, and bell pepper.
In a bowl mix crab, bread crumbs, 3 tablespoons melted butter, celery, parsley, onion and bell pepper; set aside.
Spray a baking sheet with non-stick cooking spray.
Wash, devein shrimp and pat dry.
Use a sharp knife to cut a 1/2" deep pocket in inner curved side of shrimp from tail along center, leaving 1/2" at end. Do not cut through back of shrimp. Use finger to widen pocket.
Use about 2-1/2 tablespoons crab mixture per shrimp. Place portion in hand and squeeze to mold. Place crab in shrimp pocket and distribute to fill. Place shrimp on baking sheet. Repeat, preparing all shrimp.
Brush shrimp with melted butter. Bake for 10-12 minutes. Do not over cook. Serve with a side dish of melted unsalted butter if desired.