This makes a nice clean join of two balloons rather than using two pinch twists. Tie the two balloons together and the just do the apple/tulip twist. Push the knot inside one of the balloons appox three inches, always more than you think as you will need to push the knot back towards the centre (darker balloon) so that the pressure of the balloons help to hold the twist in place.

As in diagram four where the left hand is, at this point you could tie a srap of balloon around the outer balloon to hold the knot in place before you push the knot back towards the centre of the two balloons.