Me and my friend were doing a typical King Jelly run and the 1st weird thing to happen was that he just stopped moving. Which basically everyone takes that as cool he got stuck. So then we killed him like usual but we he died all of his minions stayed so we killed them too. It acted as though we were still fighting him and where he died we could still collide with him.

http://www.youtube.com/watch?v=Ohgf_9hPZU0

This is a video of me recording what happened afterwards, don't know if it happens often but we lost energy and junk but it doesn't really matter as long as it doesn't happen again lol.

Edit: Warning video contains bleeped cursing, oh well.