Preheat oven to 400 degrees F (200 degrees C).

Place bacon in a large skillet and cook over medium-high heat until cooked through but still slightly soft, 5 to 10 minutes. Drain the bacon slices on paper towels, retaining bacon drippings in the skillet.

Melt butter in a separate skillet over medium-high heat; saute onion and celery until softened, about 5 minutes. Stir bacon and poultry seasoning into onion mixture.

Mix onion-bacon mixture and bread pieces together in a large bowl; fold in eggs. Spoon bread mixture into muffin cups.

Bake in the preheated oven until tops are crispy, about 25 minutes.