I learnt this fantastically original trick from The Juggler's Aquarium. This trick was discovered by Swedish legend Ola Lofberg. This trick is a case of discovering a throw then fitting a pattern around it I think.
Start with two balls in one hand. Grip one ball between your thumb & forefinger & the other with your ring & little fingers, just like you would hold two balls before throwing a Split Multiplex. Hold the hand with the balls at waist height. Start with the palm facing straight up, then turn your wrist inward 45 degrees so that you are holding the two balls diagonally, one above the other. The topmost ball should be on the outside & the lower one on the inside. Hold your empty hand diagonally above the other with the palm facing down. The palm of the hand holding the two balls should be pointing at your empty hand.
Now with one flick of the wrist throw both balls in the direction of your empty hand. Throw the lower ball, the one held with your little & ring fingers, straight into the empty hand. Claw it immediately after it has left the throwing hand using only the thumb, middle & forefingers. Throw the upper ball, which was held with the thumb & fore finger, up & over the side of your other hand as it catches the lower ball. Then carry the ball you are holding in an arc so that your hand follows the ball in the air. Move your arm faster than the flight of the ball so that you scoop it up into your hand just before it falls below waist height. Finish with two balls sitting side by side ready for another split multiplex throw, all in the opposite hand to the one you started with.
Practise this move with both hands alternately. You may find it easier to start off throwing the single ball from the multiplex quite high & then gradually reduce the height until the ball peaks at eye level. Make sure you get this move solid, once you can do it you've pretty much got the whole trick.
Hold two balls in one hand & one in the other. Start with the hand holding one ball & throw a normal cascade throw to the other side. When it peaks scoop & throw both balls as the multiplex throw you have just been practising. Slam one ball up into your empty hand & throw the other in between your catching hand & the ball in the air. Catch the first throw then follow & scoop up the last ball. Stop. Repeat on the other side.
What were you expecting? Something complex?
There is an extended variation that involves a few more throws.
Again start with two balls in one hand & one in the other. Make a cascade toss from the hand holding one ball & throw the multiplex move when the first throw peaks. Catch the first throw. Throw the ball that was slammed straight up into a claw catch back as a cascade throw between the ball in the air & the hand holding the ball from the first throw. Claw catch the ball that was thrown out from the multiplex. On the other side make a cascade throw then catch the ball in the air all with the other hand. You should now have one ball in the air arcing its way over to the hand that made a claw catch. Continue the downward motion of that claw catch into a carry that goes down then circles back underneath then up inside of the ball in the air. Continue the carry round & scoop up the ball in the air. Finish holding two balls in the hand that started with one & one in the hand that started with two. Repeat on the other side.