With a sharp knife, cut a thin slice from bottom of melon so it sits flat. Lightly score a horizontal line halfway up sides and around the melon, leaving 5 inches from one end unmarked on each side for baby carriage hood.
For hood, make another line around top of watermelon, connecting both sides of the horizontal line. Using the rounded edge of a biscuit cutter as a guide, mark a scalloped edge along all straight lines. With a long sharp knife, cut into melon along the scalloped lines, making sure to cut all the way through the melon rind. Gently pull off the rind. Remove fruit from melon and removed section; Cut fruit into balls or cubes and set aside.
For the U-shaped handle, cut out a 5 inch square form the removed section of the rind. Cut out the center and one end leaving a 1 inch wide handle. Break one toothpick in half. Attach handle to watermelon with toothpick halves.
For wheels, position orange slices at base of watermelon and attach with toothpicks. Top each orange slice with a lime slice and a red grape.
In a large bowl, combine the cantaloupe, green grapes, strawberries, remaining red grapes and reserved watermelon. Spoon into baby carriage. Serve with poppy seed salad dressing if desired.