Blow up a good quality latex twisting balloon and tie it off. Leave a very small amount of the balloon limp on the end.
Tie the limp end of the balloon onto the tie in the knot so that both sides are tied together. The balloon is now in the shape of a large circle.
Pinch and twist at the opposite side of the circle from the knot to make a crease. The balloon should now look like a large mouth.
Hold both sides of the "mouth" together and fold the balloon in half. Twist this whole section together. The balloon should now look like a bow tie.
Fold this in half at the twist of the bow tie and stick one side of the bow tie through the other side. The twists should be together on both ends, one on top of the other.
Twist them all together and you should now have something that looks similar to a football with four pieces linked together. It also should look like 4 bananas in a bunch, thus the name.