Add the butter to a small skillet over medium heat. Once hot, add the onion and cook until softened, but not browned, about 3 minutes, stirring occasionally. Add the garlic and cook 1 minute more, stirring constantly.
Add the onion mixture to a large bowl and stir in the cream cheese, sour cream, mayo, parsley, scallion, lemon juice, dill, Old Bay, and Worcestershire. Stir in the crab and celery.