In a food processor, combine yogurt, peanut butter and dark brown sugar and puree. Pour into a decorative bowl and chill in the refrigerator, about 20 minutes.
While the dip is chilling, make fruit "critters" using the fruits for bodies, pretzel sticks for legs, and raisins for eyes. Here are some suggestions, but use your imagination!
Quarter and core an apple. Place the flesh side down so the peel is facing up. This will be the shell for a "beetle". Cut 1 raisin in 1/2, place the inside down towards 1 end of the apple to make "eyes" for your beetle. Break 4 pretzel sticks in half and insert into the bottom for legs.
Carefully thread grapes onto a pretzel stick to make a caterpillar. Stick 2 sunflower seeds into one of the end grapes to make eyes. You can also use 2 kinds of grapes to make a multi colored caterpillar.
For a fly or bee: Cut off the last 2 inches of a banana, so you have a piece with a slight curve and a tapered end. This will be the body. Carefully stick a pretzel stick into the cut surface so half is in the banana and half is sticking out. Core a strawberry and carefully stick in onto the other half of the pretzel stick to attach the "head". Cut a raisin in 1/2 and stick the cut side onto either side of the strawberry to make "eyes". Cut 2 slices of apple and carefully stick into the banana to make wings.