This can be done for any learn-able pets across the entire account.
Step to step guide as I will also find it hard to read what I typed, so let's say you have a [Lil' Smoky] on the realm of Draenor Horde
1/ Learn [Lil' Smoky] ( Or pet of choice)
2/ check Pet journal to make sure it can be place in cage ( can skip this part)
3/ Select a realm you wish to transfer the pet/gold to
4/ Log in to the character of the faction you wish to transfer pet/gold to
5/ Enter your Pet Journal ( Shift-P)
6/ go to [Lil' Smoky] (or pet of choice) and right Right Click and select Place in cage
7/ Sell on Auction House or trade chat
For best transfer rate check the destination realm prices on the pet you're transferring, you do risk losing gold that is the only warning I can give.
Also this can be done with any pet but not pet's caught by pet battle
My Apologies if this was already posted I didn't noticed it or knew what it might of been called to search for it.
Also unsure if this is classed as Exploit or a Guide either way this is my first of many posts on Ownedcore.