In a small skillet saute onion, garlic and celery until clear. Add crawfish, salt and pepper. Simmer for 5 minutes. Grease pie plate. Add crawfish mixture. Beat eggs and milk for 1 minute. Add Bisquick, beat well. Sprinkle cheese on top of crawfish and pour Bisquick mixture into pie plate. Bake at 350~ for 30 to 40 minutes. Cool for 5 minutes. Serve warm.