Preheat oven to 400 degrees.
Soak sweetbreads in water to cover for 10 minutes; trim.
Break into 1- inch chunks.
Cook bacon until partially tender; wrap sweetbreads with bacon.
Spread mushroom caps lightly with butter.
Place sweetbreads and mushrooms alternately on skewers; place skewers over edges of narrow baking pan.
Bake for 10 minutes.