Pet ghosts

I wanted to add this to my previous post about a pet update but the character limit got me

This would have to be a rare occurrence for it to be meaningful
Imagine you're exploring a cave or wandering the overworld and you see the ghost of a dog/cat/horse you lost a few nights ago, visible to just you. It wouldn't take damage or attack mobs, but it would follow you around for a few minutes.
They could also appear:
- after you find a rare item you've been farming for

- to give slight aid if a fight gets tough (jump in from the side and absorb a blow that would otherwise kill you)

- while Gazing at a large structure you built

- after entering the end for the first time all your pets hang around and watch as you take on the dragon down.

This would add a sense of connection between the player character and his/her pets. The idea that they still follow you after they've left, cheering for you on your adventures.
This could work for any mob you can use a nametags on: sheep, pig, iron golems, fox, cow, chicken, slime, zombie.