The bug

In 1.13.2, it is possible to clone an ender dragon by somehow getting them to an end gateway block.

How to reproduce the bug

1. Go to the end.

2. Setblock an end gateway at the ender dragons Bedrock bed.

3. Go inside the Gateway once the dragon has teleported, multiple dragons will appear.

(NOTE: You can't tp back to the island, otherwise the clones will disappear)