Preheat the oven 350 degrees F. Combine the yeast, sugar, butter, and egg yolks in the bowl of an electric mixer fitted with a dough hook. Add the milk. With the mixer on low speed, beat the mixture for about 4 minutes to dissolve the yeast. If the yeast mixture doesn't begin to foam after a few minutes, it means it's not active and will have to be replaced. In a separate large mixing bowl, combine the flour, salt, nutmeg, and lemon zest. Add this mixture to the yeast mixture. Mix on low speed until it lightly comes together, then increase the speed to medium and beat until the mixture pulls away from the sides of the bowl, forms a ball, and climbs slightly up the dough hook. Remove the dough from the bowl. Coat the dough with vegetable oil. Return the dough to the bowl and turn it to oil all sides. Cover the bowl with plastic wrap, set in a warm, draft-free place, and let rise until doubled in size, about 2 hours. Meanwhile, in a small bowl, combine the cream cheese and 1/2 cup powdered sugar. Mix well. In another small bowl, combine the remaining powdered sugar, lemon juice and milk. Mix well and set aside. Turn the dough out onto a floured surface. Roll the dough out 30 inches long and 6 inches in diameter. Spread the cream cheese filling across the center of the dough. Bring the two long edges together and seal all sides completely. Using your hands shape the dough into a long cylinder and place on a greased baking sheet, seam side down. Shape the dough into a ring. Place a well-greased 2 pound coffee can or shortening can in the center of the ring to maintain the shape during baking. Press the plastic baby toy into the ring from the bottom so that it is completely hidden by the dough. Cover the ring with a towel and place in a warm, draft free place. Let the dough rise for about 45 minutes or until the dough doubles in size. With a sharp knife, make several slits around the top of the ring. Place in the oven and bake for 30 minutes, or until golden brown. After baking remove the coffee can immediately. Allow the cake to cool. Drizzle the cake with the sugar glaze. Sprinkle the cake with sprinkles, alternating colors. Cut the cake into individual pieces and serve.