This glitch can occur when throwing projectiles into portals. The details depend on the particlular projectile:

• It happens when throwing ender pearls into Nether portals. It does not happen when throwing ender pearls into End portals or End gateways.
• It happens when throwing ice bombs into Nether portals in Creative (but not in Survival). Occasionally it happens when throwing ice bombs into End gateways. It does not occur when throwing ice bombs into End portals.
• It does not occur with eggs or snowballs. I have not tested any other projectiles.
  When this glitch does not occur for Nether portals, the projectile simply phases through the portal. When it does not occur for End Gateways, the projectile shatters on the player's end, causing expected results such as an ender pearl teleporting the player.

To reproduce or test this glitch:

1. Obtain the projectile you want to test. If you are testing ice bombs, the world must have "Education Edition" enabled.
2. Create the portal you want to test. If you are testing End gateways, you will need to go to the End and defeat the Ender Dragon.
3. If you are testing the glitch for Survival, switch game modes at this time.
4. Throw the projectile into the portal. For End gateways, throw several projectiles.
5. Finally, go through the portal and see if there is a ghost projectile on the other end.

Properties of a ghost projectile:

• They look exactly like the normal projectile.
• They stay perfectly still.
• They start on top of a solid block. However, they are not affected by gravity even if the block below is removed.
• They have no interaction with blocks or other entities. I am not sure if they can be moved by explosions, but I expect that they cannot.
• They are client-side, meaning that they disappear when you exit and re-enter the game.