Minecraft baby zombie riding a zombie villager

So I was going down to my lab I made and I saw a baby zombie riding a zombie villager. Can anyone explain this?

2 Answers

According to the Wiki for the PE edition of the game:

On the Pocket Edition, they can ride other passive mobs, as well as other zombies and spiders.

This appears to be normal behavior.

2

In Minecraft mobs can spawn on top of one another and are able to stack or "ride" each other. If i remember correctly, by killing the mob on the bottom of the stack, the mobs on top of it will be released and will behave normally.