Kaizo Mario hacks will occasionally require you to juggle an item or multiple items while bouncing off enemies or jumping off of platforms and sprites like ropes. There are intricacies to the different ways this can be required of the player.
Juggling Items While Jumping Off Enemies
Sometimes, you will be asked to carry a shell while bouncing off enemies. In Super Mario World, this means the shell you are carrying can collide with the enemy and destroy the shell and enemy. To avoid this, you throw the item Mario is carrying upwards BEFORE bouncing off an enemy, then catch it after you bounce off the enemy. If you are needing to spin jump off an enemy, you will will throw the item up, then catch it while spin jumping towards the enemy. You then perform the juggle as previously laid out. It is helpful to throw the item while Mario has horizontal momentum to make sure the item moves forward with Mario so you can catch it again. If you are on a slow moving enemy, you may want to throw it while Mario isn't moving as fast, you must learn to manage this based on what the situation requires.
Juggling an Item While Jumping off of Ropes
You cannot grab line guided ropes while holding an item. If you need to carry an item through ropes you will need to throw the item up, grab on to the ropes, jump off the ropes, and grab the item again. It is very helpful to hold up the entire time during these juggling sections with ropes.