Info on the Chopper Split:
The Banana usually disappears after 1 bike ride off of the stage, so if missed, it's unlikely that you'll be able to do it again with the same banana. Unless, the Diddy has just pulled out the banana. It can be attempted twice max for one banana.
You can control the direction the banana goes in. Let's say that Wario is biking from left to right. In this case, if you hit it on the left side, the banana will fly towards the right side and upwards. If on the right side, the banana will fly backwards and to the left, upwards. This can mean that you can have a banana fly offstage, or onto a platform. Timing is tricky, however.
The banana is still in Diddy's control after the Chopper Split is activated.
Wario is stunned after this! He can't use an attack, special, item toss, or airdodge until he hits the ground! He gets knocked in the same direction he hit the banana. If he hits on the left side, he goes left. If he hits on the right (and he's moving left) then he'll go right and turn around.
Does not work if he's biking in the air. (We can't get gimped from this!)
Does not work if the platform is too high (BF or Brinstar's top platform.)
Does work if you bike from another platform.
Does work if it's on a tilting or moving platform.