Cut jalapenos in half and remove seeds. Place in two ungreased 15x10x1-in. baking pans. In a small bowl, combine the cream cheese, cheddar cheese and onions; spoon into jalapeno halves. Top with shrimp.
Bake at 400° for 18-22 minutes or until jalapenos are tender.
Wear disposable gloves when cutting hot peppers; the oils can burn skin. Avoid touching your face.