Pushing a Pokémon through a nether portal will return the Pokémon to your hand as well a reporting it through thus making a duplicate.

Steps to reproduce:

1. Throw Pokémon out.
2. Push it into nether portal
3. Pokémon will return to your inventory
4. Now go through portal and recall the duplicate.

Forge 1965
Pokecube core 3.24
Pokecube mobs 2.12
Pokecube revival 3.22

Modpack: Infinix test
Minecraft: 1.9.4

Temporary fix for this will be to prevent pokemobs from passing through nether portals. Will have that fix in the next release, I will work in a more "proper" fix later, as this bug will probably also affect end portals and modded portals.

Uploaded the temporary fix for this in http://minecraft.curseforge.com/projects/pokecube-core/files/2309016 (may still be a few minutes before it is available)

I will leave this issue open as a reminder incase it does occur with other portal types.

This issue also applies to End portals. Similar method of pushing them into the portal, then recalling the Pokemon, and proceeding into the End and finding a copy of the Pokemon.

Version 1.9.4/1.10

Found cause and fixed now :D