As far as I can tell, this trick only applies to the purely visual slime effect, and doesn't seem to work on any other buffs, which is why I feel okay sharing this. It should go without saying that if you happen to find some way to abuse this and obtain some damage-boosting buff like what has been possible in the past, DON'T use it.
Some examples:
Works on buff pets too, without affecting their existing buffs:
Here are the steps:
1. Go to Maldraxxus (Plaguefall probably works too) and stand near one of the massive slime lakes. A good spot to do this is 60, 72.
2. Use Eyes of the Beast to control your pet.
3. As your pet, jump into the slime lake, and swim as far away from your character as possible, while remaining in the slime. Keep going until the channeling ends on its own.
4. Your pet should despawn automatically. Call it out again and it should have retained the slime appearance.
If this doesn't work (it seems that sometimes, your pet can just teleport back to you), you can try this method instead:
1. Stand near a slime pool.
2. Use the "Move To" command to move your pet into the slime.
3. Run away from your pet until it despawns.
4. Call it out again, it should have retained the slime appearance.
Enjoy your slimy friends!
