odd couples

I have a fire urchin and two of my fish the last few days have fallen in love with it. First it was my porcupine puffer. He would lay next to it on the sand while the needles would touch him all over and it would even stick its little sticky strings in the puffers mouth. We thought maybe the puffer thought it was another puffer or something. haha

Then, all of the sudden our orange striped trigger started laying down where the urchin was so it would crawl on top of it. I think the urchin even bit it a few times because you could see the trigger get spooked and try to get away.

Anyone ever have something like this before or know why?